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Heating Ventilation and Air-Conditioning - Science topic

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Imagine that you start a simulation where you need to compare different schemes, models and mesh for the same problem.
How would you organize the files and where would you compare the data?
For example, let's take an HVAC example where you need to change the flow rate to try different turbulence models and Mesh. Easily you could get something like:
HVAC - Mesh 1 - k-e
HVAC - Mesh 1 - k-w
HVAC - Mesh 2 - k-e
HVAC - Mesh 2 - k-w
Then let's say you want to show all the results together and easily compare how would you do it?
So far I just manually save PNG and compare in a table of pictures using word. How would you do it?
Thank you,
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First, I would recommend NOT using png. Journals usually require high-quality vector graphics, so vector eps/pdf should be preferred.
If the comparison is visual, then you might show an array of figures like
mesh1 k-e mesh1 k-w
mesh2 k-e mesh2 k-w
Although presentation of results is mostly a subjective matter, I would arrange smaller figures closer and easier to compare rather than large figures far from one another. This depends a lot on the kind of comparison you have to perform, however.
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I am working in a HVAC project that includes a NMR 300, I found out that it cools down by liquid helium or liquid nitrogen so i want to know the amount or the range of heat rejected to the surrounding
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Dear Omar,
Interesting question....I never thought about it. If once the cool-down is done (only done once while installation of the machine) the calculation for "regular operation" can probably done like this:
Latent Heat of Evaporation of N2 is 200 kJ/kg. If we assume a loss of 100 l per week (actually it is lower for a 300 MHz machine) we end up if I calculated correctly about "30 W" of "cooling power" 200.000[kJ/kg]*0.8[kg/l]*100[l/week]/(24[h]*7[days]*3600[s])..I'll guess the He contribution can be neglected, but the electronics of the console adds a few hundred watts.
So at the end for a decent air-conditioning no problem!
I hope I calculated half-way correctly
Alfred
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Dear researchers, I am currently working on a project with the aim to design a small-scale pellet stove for residential heating applications. Before making a prototype, I am required to develop a mathematical model that describes heat transfer phenomena inside the pellet stove and do a simulation about it. I'm having a hard time finding a consistent mathematical model in the literature that complies with my application. Do you know any good references that did similar work with pellet stoves or any biomass boiler in general?
Thanks in advance.
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Thank you Dr. Hanasoge Mukunda for your answer. The building heat transfer calculations are not very complicated as you mentioned. What I want is how to model the combustion of the pellet stove in order to get the required fuel temperature to ensure thermal comfort in a small space.
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I was going through properties of refrigerant R134a ,from different sources ,I found at the same saturation pressure and temperature ,enthalpy and other parameters were varying too much in the two different sources. Why ?
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Thank you. I agree
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explain your idea
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Explain your question.
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Hello,
My reseacrh area is absorbtion refrigeration system with nanofluid. I know how can I calculate the performance parameters of NH3-WATER and LiBr-WATER as a base fluid. But the thing is, how can I integrate the nanoparticles to basefluid to calculate the performance parameters theoretically using Engineering Equation Solver ? I found some articles but they were useless. After adding nanoparticles to base fluid to make a nanofluid, how can I calculate entalphy, entropy, mass flow rate, COP, circulation ratio, variation of rich and poor concentrations, condenser and absorber capacity ?
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explain your idea
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I am wondering if some software such as EnergyPlus provide their codes behind the scene of their fan calculation freely available. (no matter in which programming language)
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Thank you so much Ramon Weber
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hi
i want to do a simulation of HVAC system of building using TRNSYS but i need to create the weather file of my city ,i try to use meteonorm but i didn't find a free download for windows 7, please i need the software or a different way available for TRNSYS
THANK YOU!!
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You can also find the EPW files (and other formats) at:
This is a repository of free climate data.
Kind regards,
JL
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When designing AHU what is the criteria of using or not using mist eliminator?
It says in the attached image (if required).
Please provide any standards/references.
Thanks
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Also check please the following useful link: https://www.sciencedirect.com/topics/engineering/mist-eliminator
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I need to build a virtual AC model from which i can generate the necessary outputs, such as total power consumption with respect to time and so on
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The commercial available software are very expensive. Please refer the ASHRAE manual and create the simple program through EXCEL. Then, it is more convenient you to alter.
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Specification for use
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Thanks all
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Hi everyone, I have attached a picture of sketch for FCU duct-borne noise calculation. There are 2 questions in the sketch or as shown below,
Q1: Do we do power division for the FCU sound power when calculating duct borne noise for path 1 and path 2? Any published material for referencing specifically for this?
Q2: SPL at receiver = Path 1 + 3dB or Path 2 + 3dB ?
I'm welcoming any advise and comments towards it. =)
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Jack Chong , i guess you need to ask / understand exactly what is specified / given in that spec respectively how it was measured to understand how you could make use of the data given.
I am very well aware of poor specifications, incomplete understanding of acoustics by people distributing such data, etc.
However, I think we cannot really help you here within this discussion without more detailed information. At best, we might add further guesswork - and I am doubtful whether that would help.
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Hi all,
I am working on a HVAC project where many components(cooling coils, pumps, etc) needs to be modelled newly(new equations), and in addition new hydraulic connections. And EnergyPlus needs to be used for the overall system level simulation. For that I have to write/include the new equations into EnergyPlus. I have heard that the codes in EnergyPlus are written in C++. Problem is I haven't been able to begin with a good start. Primarily- Where do I go to edit/add new codes? ,and how do I create new Hydraulic connections between components? If you could point me to a direction, that would be hugely beneficial.
Thanks
Regards
Asutosh Boro
PDEng researcher Eindhoven University of Technology
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I totally agree with my colleagues
good luck
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In ASHRAE design conditions, should we use annual or monthly climatic design conditions for cooling load calculation and equipment sizing?
In McQuiston [HVAC book], only the annual are used, so what monthly design conditions are used for?
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Hello. Annual information is used to determine the energy consumption of the annual cooling and heating load. But to know, for example, how effective the impact of insulation can be each month, you need to use monthly weather information.
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Dear colleagues,
I am developing an HVAC MIMO model, through writing the state equations I am facing the attached state equation where in the third term, two states are multiplied in one term which creates a non-linearity in the system. The equation (part of eleven state equations) is attached
a,b,c and d are constants while (Tcc) is the cooling coil temperature, (Trfrgnt) is the temperature of the refrigerant (qsa) is the mass flow rate of the blown air, (Tra) is the temperature of the recirculated air and (To) is the ambient temperature
Now I face a problem of how to establish the A matrix (11 x 11), what is the best way of linearization of this particular equation? Do I need to linearize only the nonlinear term in the equation? Once linearized, does the linearized process effect the other state equations?
Kindly support and advise
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Thank you sir, I will be sending you an email right now.
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An air-cooled evaporator will be placed in a room and the evaporator temperature will be -40oC. What should be the air temperature to and from the cold room to the evaporator? The screenshot is attached. Thank you.
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Ali Dawood Salman thank you very much. In this case, will the temperature of my room be -28oC or -34oC?
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explain your idea
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explain your idea
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It is necessary to react not only with administrative solutions against pandemic situations like the case with Covid 19.
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Hi dear Arda.
Outbreaks appear to be exacerbated during urban sprawl, with new coronaviruses causing increased surveillance, overcrowding, and new activities in the community.
In some cities, contaminated neighborhoods were cleared, early quarantine facilities were expanded, and public spaces were enlarged and improved.
As the prevalence of the epidemic increases, the most important need in architecture is the speed of construction of disease control areas such as hospitals, quarantine centers, wards and temporary accommodation.
- Use of buildings for multiple purposes
The results of studies on coronavirus showed that some buildings can be quickly converted into accommodation centers for patients or even a hospital, and this indicates the use of buildings in the most efficient way to create emergency facilities.
- Designing a healthy building
On quarantine days when you are mostly at home, you may pay more attention to the shortcomings of your living environment than ever before.
The Healthy Building Movement can be an effective approach to improving health through strategies such as more natural light, improved ventilation, and greater use of plants and natural materials. The use of large windows, terraces, roofs and courtyards has become more prominent in these cases. Places for exercise and meditation at home should be more standard.
Also, following health tips in some places where social distance is not usually observed, such as prisons, homeless shelters and nursing homes, can be effective in reducing the prevalence of epidemics.
The use of antimicrobial strategies such as antimicrobial polymer surfaces and copper alloy surfaces that naturally kill germs and viruses is very important in these cases.
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I am trying to model a desiccant dehumidifier in EnergyPlus based on the examples that this software provides, but I am needing more information about this.
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Dear all,
My research group is currently working with a 12-litre fermenter. Somehow, if we do the fermentation for more than 20 hours, the process will be more prone to contamination. Our current suspect is the air vent filter. As we live in a tropical country, the humidity is quite high (40-50% with the HVAC system). The current material of the air vent filter is PTFE. Have you ever experiencing this problem before? Thank you!
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Hello, you can chech your vent air by passing trough liquid media in falsck for 1-2 hour and then see any grow after incubation of flask about 48hour.
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Heating Ventilation Air-conditioning System related thesis topic for thesis
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HVAC is a very broad topic. Step 1 of formulating a thesis topic is understanding what current research is addressing and what the current gaps are in that knowledge base. I suggest finding a few review papers to get a high level understanding of the field, then when you find something interesting you can dive in deeper. Some suggestions taken from the first three pages of Google Scholar results for "hvac review":
An overview of HVAC technology development over 30 years:
Automotive HVAC systems review for electric vehicles:
HVAC modeling methods:
HVAC Energy savings strategies:
HVAC Optimal control strategies:
HVAC dehumidification technology:
HVAC impacts on indoor air quality:
HVAC technologies focused on thermal comfort:
Phase change thermal storage for HVAC systems:
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How to write the fuel and product exergy balances in the cascade heat exchanger in the cascade refrigeration system?
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The definition of fuel and product exergies depends on the chosen reference temperature. For a heat exchanger, possible formulations of fuel/product exergies are shown in the attached figure.
For more detailed information, you can have a look at the following publication:
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Dear fellow friends, are there any good and PRACTICAL references for above subject matter? which can show real life problems and calculations. Thanks
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Yess, i have,plesae write me on jasrash55@gmail.com
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Variable-speed-compressor refrigeration systems were examined by many researchers for minimizing energy consumption. The results were interesting. However, this technique may be possible for new designed systems. My question is about systems which are in service right now.
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Use the frequency invertor .
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Hello.
I would like to know if smart HVAC is the same as measuring temperature and Humidity or there is a clear explanation on this as I am working on a smart HVAC system as part of a smart home.
Regards,
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In a smart HVAC system for home not for a building, the system should provide (1) monitoring by smart devices and web browsers, (2) room-wise temperature/humidity control, (3) smart/remote metering, (4) energy saving and scheduling, (5) remote boiler and AC maintenance and (6) smart ventilation control. Adopting IoT sensors are an option but will allow easier implementation.
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I'm using OpenFOAM to run a CFD study of thermal comfort within a hall. I'm using OpenFOAM v1912 and BouyantBoussinesq(Simple&Pimple)Foam solver. eI have 6 inlets and outlets each with specific flow rates. I specified the flow rates accordingly at the inlet using flowrateinletvelocity BC and at the outlet using flowrateouletvelocity BC. Based on the height, I computed (p-rgh)/rho and fixed it at one of the outlets.
My mesh quality is good (Non-Orthogonality less than 50). The dimension of my hall is 30m *30m *4.5m. It was okay so far when I was doing the simulation for small halls, but I'm facing this problem at the moment.
This happens each time I start the simulation, at the beginning of iterations, p rgh iteration (1st step) reaches 1000 or 2000. The final residual is very high (greater than zero). After the cumulative value (continuity error) begins to rise and becomes greater than 1. The value of Pressure ranges from 1e18 to -1e18 (Two extreme values) even after after 1 or 2 time steps, then the simulation blows off.
I have tried the following options
1)potentialFoam initialization
2)Mesh quality check
3)Defining pressure at all the outlets
4)Using prefcell and prefpoint in fvsolutions to define the pressure in fvsolutions.(if I use this I get continuity error at the start of simulation)
5)Both steady state and transient analysis
6) keeping URF very low and also reltor for pressure to 0.0 in fvsolutions
7)first order and 2nd order fvschemes
7)nNonOrthogonal correction raised to 20.
8) I have turned off turbulence.
9)simplifying the geometry.
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I sorted the issue.
1) Yes your correct, but in HVAC there will be exhaust fan that sucks at particular rate. So if we let the flow dynamics to determine, then there is a chance more flow goes to one outlet than other outlet which might change the streamlines. Also in conventional CFD problem, the flow develops and leaves from one outlet. But here we need specific flow rate at each outlet. Also as there is an option (boundary condition) in openfoam to define flowrateoutletvelocity.
2) Yes as you said p-rgh is computed as you said. We have to define it based on the overall height of the domain, then only hydrostatic pressure will be computed correctly. I do accept it is constant, but if we define it 'zero' then the pressure will become negative.
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Is there a way to ask manufacturers some data to be available to the public for the scientific community analyze?
For example, in this COVID-19 pandemic, many researchers are trying to find the best solutions of HVAC to renew and reroute the air as much as possible. However, the only way to do this is if they have the specific data from the HVAC companies, like the CAD data of the inlet as well as the mass flow rate, and outlets.
If we don't get that data, then some independent researchers need to experiments to get the data and then be validated by cfd until convergence, which would hopefully be good enough and extend the length of the process.
Is this the way how to do things? Or are there ways that companies share their data?
- In my case, my industry of interest is aviation/aerospace.
What inputs do you have?
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It will be very difficult to attain operational HVAC data since control in HVAC is mission-critical and its failure would be sometimes disastrous. If a high-rise building is of interest, a SCADA system would be in charge of handling the time-series data from all the subsystems. Inherently, these data are collected to improve the operational efficiency of the system. So, the supervisor might be interested in the simulation results although would be reluctant to publicly open such data. Rather, application of industrial IOT to the HAVC raises concerns on security bleach.
I think there are very few fields where industrial data are available to researchers. However, by a consent from the owner or the supervisor, a researcher can collect sensor readings, which can be from operational system or from sensor readings out of the control loop.
Articles say the HAVC systems become smarter and smarter, but in the real world, it seems just a part of a real estate. The 20-30 year old FCUs are still in use and designs of diffusers and ducts seem to never change. The owner might not like to let more air in because it will increase load in temperature and humidity control. The main drivers of this industry appear to be regulation and stability.
Good luck in your overcoming the gap!
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Dear all,
Which are the most applicable models to analyze the energy effect and thermal comfort?
Models applies especially to occupant-controlled, natural conditioned spaces, where the outdoor climate can actually affect the indoor conditions and so the comfort zone
Many thanks in advance
Elena
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You can find a good summary of the thermal comfort standards we use in our research in this paper: https://www.mdpi.com/2071-1050/12/22/9630
It includes criteria for naturally and mechanically ventilated, both with fixed threshold and adaptative models.
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I'm working with the OpenStudio Plugin to generate an IDF in order to use it as input in an EnergyPlus simulation.
I'm working with a 1-story building, with 5 rooms, a VRF System and 3 VRF Terminals.
After exporting the IDF, when I run the simulation I obtain these three warnings:
1. VRFCOOLCAPFT output is equal to 1.136 at rated conditions (instead of 1.0):
** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF SYSTEM" curve values
* ~~~ ** ... Cooling Capacity Ratio Modifier Function of Low Temperature Curve Name = VRF SYSTEM VRFCOOLCAPFT 1 output is not equal to 1.0 (+ or - 10%) at rated conditions.
** ~~~ ** ... Curve output at rated conditions = 1.136
2. COOLINGEIRLOWPLR minimum value of X = 0.500 is out of range. It must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF SYSTEM", invalid
** ~~~ ** ...Cooling Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = VRF SYSTEM COOLINGEIRLOWPLR 1 has out of range value.
** ~~~ ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
3. HEATINGEIRLOWPLR minimum value of X = 0.500 is out of range. It must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
** Warning ** GetVRFInput: AirConditioner:VariableRefrigerantFlow="VRF SYSTEM", invalid
** ~~~ ** ...Heating Energy Input Ratio Modifier Function of Low Part-Load Ratio Curve Name = VRF SYSTEM HEATINGEIRLOWPLR 1 has out of range value.
** ~~~ ** ...Curve minimum value of X = 0.500 must be <= Minimum Heat Pump Part-Load Ratio = 0.250.
_________________________________________________________________________________________________
So, finally, I obtain the fatal error here below (caused by the three warnings above):
** Fatal ** GetVRFInput: Errors found in getting AirConditioner:VariableRefrigerantFlow system input. ** Preceding condition(s) causes termination.
Then, EnergyPlus terminates.
Is there anyone who could help me?
PS: If useful, I could attach the IDF.
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Hello. Sometimes it may be useful to increase or decrease a little bit the cooling capacity of the equipment (ex. If it is 12000 BTU/h, change it to 11500). Also, you can modify the COP of the system. I have used these tips when working with HVAC systems in E+.
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I have a project with three sections:
the first asked me to calculate the Hb ( Building loss co-efficient) and Tb (balance temperature ) using the variable degree-day method. To do this, I calculated the degree days and the energy consumption for each month. Then used a linear relationship to find Hb & Tb. and that's done.
The problem is with the second part of the question. It asked to calculate the energy consumption when the building loss co-efficient decreases by 15 percent. I am going to use this formula 𝐸𝐻,𝑚 =24𝐻𝐵/ thermal efficiency* V (volume of the building) * [𝐷𝐷𝐻,𝑚−(18−𝑇𝐵)𝑁].
However, I do not know how to calculate the new Tb for the building ??????
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Hi Matt
A simple method is presented for accurately computing the degree-days to any base temperature. The method is based on an assumed annual normal distribution of the daily mean temperatures around the monthly mean temperature. A maximum of the prediction error of only 0.28 degree-days per day was observed when compared to actual weather data at four representative locations.
for more details check this:
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When you keep inside a central HVAC equipped building, you are breathing the same air with all patients inside that building..?
You are sharing the same disease.
The confined/contaminated air comes to you with the cooled/heated air inside the normally closed building. You receive all pains through air ducts.
-
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I am looking for a formula to calculate specific temperature drop in duct based on airflow, knowing the specific power loss, airflow, thermal properties of the duct, and air temperatures. The goal is to be able to produce the graph attached.
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I can digitize the curves and obtain a formula that will accurately reproduce them if that would help. It doesn't tell why or reveal the basis but it's something, perhaps a step toward achieving the ultimate goal.
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is it possible to calculate the return air temperature in the system if no heat gains and losses are taken into account (except for temperature rise due to the fan) knowing the supply air temperature, temperatures of different ventilation zones, airflow, and outdoor temperature?
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Dear Nadeen
I do not have time to prepare a detailed description of the whole method and assumptions. However, I think you are rather looking for equations like in the appendix.
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There is evidence that Increasing indoor humidity reduces the spread of influenza virus and probably SARS-CoV-2. The mechanisms discussed in the literature include promoting the action of the cilia of epithelial cells in clearing pathogens, reduction of the stability of lipid-enveloped viruses in aerosols and on surfaces, and slowing the evaporation of cough droplets, causing them fall faster and spread less. Indoor relative humidity typically decreases in winter as cooler air from outside containing less water is heated. This may cause the seasonality of flu. Are humidifiers underutilized tools to help prevent a resurgence of COVID-19 this fall and winter before medical interventions are available?
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So I found the answer to my question after some, well, research. See
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I am interested in the literature that addresses negative temperature lift during vapor compression. Can someone also recommend literature regarding air conditioning of interior rooms within large buildings that require year-round cooling? We are trying to address the negative temperature lift in our VCC model (which uses ice as PCM integrated with HVAC system), and this scenario seems to be a relevant case which I can take as an example.
Thanks
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Thank you
Fred Betz
and Hassan Nasser for the answers. These are helpful
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Based on information of a certain room, like room's volume in m3, dry air specific heat and dry air density. How can one calculate the temperature if we know how much thermal energy is present in the room.
Information needed to study HVAC systems.
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Energy = mass * Specific Heat * Temperature Difference
However the air in the room is never dry, therefore the psychrometric charts are needed to accurately calculate the energy content as a function of the properties and humidity.
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UVGI technology has long been known to be an effective tool to fight against airborne infectious viruses. However, lower wavelength UV light source (<240 nm) is also known to induce Ozone production from oxygen in the air. In addition, UV light is known to have carcinogenic and cataractogenic effects. UV lamps of wavelengths in far-UVC range (207 to 222 nm) and low dosage (2 mJ/sq.cm) have been studied to have an effective germicidal effect by neutralizing viruses and bacteria without adverse health effects to humans. Far UVC has emerged as a promising technology in the recent years ( https://www.nature.com/articles/s41598-018-21058-w ). While the use of wavelengths higher than 240 nm can be incorporated in enclosed systems like air purifiers and HVAC which can minimize direct skin and eye exposure of humans to UV light, far UVC has additional advantages of usability in open configuration in public places.
What are some other known real-life challenges and other important issues associated with UVGI technology to be cared for while designing systems integrating HEPA/ULPA filtration to be used in portable air purifiers, HVAC systems or upper room UVGI lamps in hospitals, commercial and residential buildings specially in the context of fighting the rapid spread of infectious viruses like the coronavirus associated with COVID-19?
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The following may have useful information
Deleted research item The research item mentioned here has been deleted
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I am currently working on thermal wheels in HVAC system and developing an analytical model to obtain the operating parameters. I need a help how you are working on these devices
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Dear Dinuka
There are traditional methods based on non-dimensional parameters to model them. You can find these methods in text-books (e.g. in HEDH there is one).
For designing a thermal wheel you should calculate these parameters for your case (inlet and outlet temperature and mass flow rate of hot and cold streams):
+ Inner and outer diameter of wheel
+ Length of wheel
+ Porosity of it
+ Rotational speed
+ Matrix material (Cp, conductivity, density)
+ And some other parameters (e.g. ratio of hot area (its default is 50%), ratio of flow area to total cross section area, ...)
You may consider different leakage flows by calculating them or simply assuming a value for them.
You can find various designs for a specific case satisfying your thermal duty. However, each of them may differ in pressure drop, weight, and other important features. So you may need an optimization or at least choosing the best option among a dozen of designs. Obviously, your optimized thermal wheel may be different based on your cost function (your goal).
You can read my article here:
Its references may also help you.
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The air flow from hot to cool creates condensation that leads to potential health hazards from pathogens trapped in the inner working of an HVAC system. UV and Plasma Air Technology both go after these pathogens. Filters used in the HVAC system stop contaminants but also can actually trap organic materials where they may grow and increase the health risk.
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It's a good discussion...
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In order to reach a desired cleanliness level inside the cleanroom, the HVAC system combines air changes per hour (ACH) with HEPA filtered air circulating into the cleanroom many times per hour.  ACH can be calculated by dividing air volume supplied per hour by volume of room.
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Cleaning validation
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Hi,
I would like to know more about practice-oriented journals for control systems application in: HVAC, industry, process systems, chemical processes, oil&gas etc. Majority of the Control journals are theory oriented, the most practical one is CEP (Control engineering practice), of course as the name suggests.
I need more titles like this. And also if some non-control dedicated journals cover various experience with applied control systems in some particular industrial field, please share.
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You can check journals list and their ranking here https://www.scimagojr.com/journalrank.php?category=2606
Best regards, Amin.
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Hello,
Does anyone have electronic version of 2017 ASHRAE Handbook and AHSRAE standard 55? It would be a great help if someone can share these two useful tools. My email address is lmhtongji@berkeley.edu. Thanks a lot!
Best regards,
Maohui
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Dear followers,
Thanks for your trust and help to share the ASHRAE handbook. I have sent the book to over 30 requests individually by email. For the convenience of future requests, you can find the book through the link below. If you have problems to open the link, welcome to give me an email.
Best regards,
Maohui
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Please complete this questionnaire
Name:
Age:
Office type: Open space office/closed office
HVAC system: Yes/No
Natural ventilated NV: Yes/No
Season: Winter/Summer
Climate zone:
Thermal comfort scale
-3 Cold
+2 Cool
+1 Slightly cool
0 Comfotable, Neutral
+1 Slightly warm
+2 Warm
+3 Hot
Thank you a lot.
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Name: Roulet Claude-Alain
Age: 79
Office type: closed office
HVAC system: Yes Heating only, by radiators
Natural ventilated NV: Yes
Season: Winter
Climate zone: Central europe (Swiss Plateau)
Thermal comfort scale
0 Comfortable, Neutral
Thank you a lot.
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If I want to calculate the energy use of an AHU fan, knowing the maximum airflow, fan efficiency, and static pressure, what would be the most accurate way?
Thanks!
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I fully agree with Paul, as long as actual airflow rate and the corresponding actual pressure difference are used.
More info on fan and system curve on https://www.cibsejournal.com/cpd/modules/2011-11/
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This refers to modelling for VAV and HVAC systems
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Hi there
In general two two connected lines with different slopes referred as bilinear.
Regards
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I am developing a TRNSYS model for a single air cooled chiller with an expected load, however having some issues.
Does anyone have any examples they can share?
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I strogly recommend you to use following like to join TRNSYS-users and get your answer from highly experts in TRNSYS modeling:
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I am working on a HVAC energy consumption optimization matter
I want to use energy simulation programs such as IES or energy plus, the problem is that I need to run at least 10 thousand simulations with different inputs Which is not possible to do manually Therefore I wanted to know is there a possibility for changing the inputs in a predefined range with predefined steps and running simulations in an automative way?
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You can use EnergyPlus using the following steps:
1)You need to write a custom application by using programs such as Python, C Sharp, etc.
2) Reading a base IDF file, which is the format utilized by EnergyPlus which describes the simulation parameters, including mechanical systems operation.
3) Using the ANTLR platform, the parser will be created .
4) Having parsed in a text file and having it converted to programming objects, selected parameters will be changed using a combinatorial sequence and for each parameter a separate IDF file will be created.
5) Finally, each of these created files can be run through EnergyPlus across multiple computers or just using one supercomputer.
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Real-time optimal control is widely adopted in central heating, ventilation and air-conditioning systems to improve the building energy management efficiency by adjusting system controllable variables (e.g. chilled water supply temperature) according to system operating conditions. In literature, there are generally two types of methods to trigger the HVAC optimal control: (mostly is) time-driven optimal control and (some is) event-driven optimal control.
In time-driven optimal control, optimal control actions are triggered periodically, e.g every 1 hour trigger an optimal control. In event-driven optimal control, optimal control actions are
triggered by “events” instead of a “clock”, which creates non-periodic control.
I was wondering what are the triggering methods of HVAC optimal control used in engineering projects? As reported in the literature, most practical projects adopted time-driven optimal control. Some engineering projects may use the so-called rule-based method to trigger optimal control (indeed rule-based method belongs to event-driven method). The rule can be pre-defined in building automation system or sometimes defined by human operators to decide a experience-based rule and operate the optimal control manually.
This is what I have learnt from the literature. I am not sure whether this is true in actual engineering projects. Pls leave a comment.
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Thanks for your comment.
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Informations
What are the keys of thermal comfort in your office?
Describe your office how it is,
If you need to use an HVAC system,
What about your adaptation?
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Dear Ahmed,
I can say that my office is very uncomfortable in summer because there is no thermal insulation or sun breezes without adding that it is well oriented towards the sun (East-West), so intense radiation and great heat which really requires the continued use of air conditioning.
Best regards.
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A certain amount of heat can be exchanged by various combination of m and dT. There is a combination of it to get the lowest electric power consumption.
I think, if we can adjust the active amount of refrigerant in the circuit by real time, we can use this equation.
Don't you think so?
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Following
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I am looking for binary diffusion coefficients of water vapour in air at normal pressure for various water/air temperatures. I found the following relation
Diff (T) = 22.5*10-6 (T/273.15K)1.8   [m2/s]
However, no reference is given, where it comes from. Do you have an equation or coefficients in tabular format or a reference for the formula shown above?
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You are right, Mohiuddin Ahmad. But this is a problem of the Researchgate web-site. The '-' disappears and reappears depending on the format in which you view the initial question. Better this way?
Diff (T) = 22.5E-06 * (T/273.15K)^(1.8)   [m*m/s]
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Hello everyone! 
I am just about to take part in a refrigeration system design competition but unfortunately it is my very first time stepping in the real world of engineering & I do not know exactly what are the steps of designing a one-stage vapor compression refrigeration cycle. The system I should design must be able to handle the followings:
1-cooling down a 50 L of water storage from 28 C to 7 C at a minimum time duration.
2- Constraint: compressor power must not exceed 600 W!   
I would deeply appreciate you if you could help me through.
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This is a heat transfer rate maximization problem in the evaporator , in which you have to find an evaporator with the maximum LMTD which means the highest efficiency. Theoritically you can cool down the water as fast as you want but you have design restriction such as refrigrerant inlet temp to the evaporator. In the best scenario the refrigerant inlet temp to evaporator cannot be higher than 2c for your design case and it leads to local water solidification which acts as an insulator. To solve this problem you can recirculate water in tank or add antifrost to tank if you are not using it for sanitary purposes. Higher evaporator efficiency inflicts alot more costs.
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What if we can know when a space/zone in a building is occupied (time, duration, preferences among others)? Will that information help the building mangers to improve occupant comfort?
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Additional Clarification: Spatial entropy can be dependent on different variables. The most important one is occupants. The entropy changes can vary based on how many occupants are in the given space and for how long. It is important to design controls based on occupant factor to maximize comfort.
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Informations
What are the keys of thermal comfort in your office?
Describe your office how it is,
If you need to use an HVAC system,
What about your adaptation?
Your age, Sexe, positoin,
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Being able to perform office task without transpiration.
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Hello All,
First I hope you doing well,
I am looking for an MPC Matlab code for energy/heat/HVAC optimization please, or anything related to MPC in the house energy consumption.
Thank you in advance,
Sincerely,
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Thank you !
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i'm a student , and i'm interested for study havc ,plumping and fire fighting design , and i search for good content in it instead of taking a course
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Dear Yasmeen
Every HVAC design involves, as a first step, a problem-solving process, usually with the objective of determining the most appropriate type of HVAC system for a specific application. It is helpful to think of the problem-solving process as a series of logical steps, each of which must be performed in order to obtain the best results. Although there are various ways of defining the process, the following sequence has been found useful:
Please feel free to contact me for any inquiry
Prof.Dr. ahmed sharaf abdelhameed
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For my thesis, I'm performing LCA analysis for different HVAC systems, for a building in Sweden. Therefore, i was wondering what would be the most appropriate software and database to use?
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OpenLCA or SIMApro and EcoInvent v3.3
E
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HVAC systems common in tall buildings, e.g., VAV, VRF, etc.
Data about various stages (cradle to gate.. to site.. operational... maintenance... to grave.. to cradle)
Already found the following article. Any other one would be appreciated.
(COMPARISON OF THREE HVAC SYSTEMS IN AN OFFICE BUILDING FROM A LIFE CYCLE PERSPECTIVE Shuo Chen et al.)
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Dear Yusuf,
The papers aren't directly relevant to the question. Are they?
Thanks
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I design a project 3TR solar vapor absorbtion air conditioning system (NH3+H2O) driven by flat plate collector. The system required 120℃ temperature by collector.
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It is something difficult but it is not impossible. Please take into account an example:
nth=Fr(ta)-FrUl*(Tfm-Tam)/GT
Fr(ta)=0.8
FrUl=4
The previous are generally high values.
In this case, the thermal efficiency is zero if (Tfm-Tam)/GT=0.2
During a summer day, maybe there is Tam=30 and GT=900 for example.
In this gase, the maximum possible operating temperature or stagnation temperature is 210oC. So, you can see that this temperature level is over 120oC that you ask.
More specifically, in your case, for Tfm=120, the thermal efficiency is 40%.
So, for achieving operating at 120oC you need:
a) A high efficient FPC
b) High solar potential
c) High flow rate in order to have maximum FR
d) Operation with a fluid which can be liquid at 120oC. For example pressurized water, thermal oil, or EG for instance.
However, you have to take into account that FPC are mainly used for applications up to 90-100oC, but in some cases they can operate more than 100oC.
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What is appropriate heating and cooling thermostat set points (and set backs) for large open office spaces? (It's a tall office building in tropical desert climate of Dubai. The interior humidity ranges between 45-55 percent)
I would appreciate if you could reply referring to valid standards or academic literature.
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Here is a tool you may want to use.
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Hi
How can I calculate run fraction (Fc) based on bin method in ground source heat pump?
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Generally, run fraction calculated by degree days method. The following may be help you.
Shen, B., Baxter, V., Abdelaziz, O. and Rice. K. (2017). CCHP –Finalize field testing of cold climate heat pump (CCHP) based on tandem vapor injection compressors (Regular)– FY17 2nd Quarter Milestone Report. OAK Ridge National Laboratory. Page 5.
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In particular I'm looking for books/articles (preferably with free access) which compare ASHRAE standards to European Standards.
I found the following article helpful:
What other sources do you suggest? It would be great if they cover these keywords: large office buildings, tall buildings, (various climate zones including) hot climates
Thanks
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Dear Aryan:
Attached please find some suggestions:
I hope that this information is of help to you.
Arturo
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Hello, I have a question about the last version of Airpak. Airpak is a precise
and fast responding software that is exclusively used for ventilation
cases and has a vast ability to present the temperature contours, velo-
city vector and stream lines and evaluating the indoor thermal comfort.
My question is:
What is improved in Airpak 3 compard to Airpak 2?
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GUI of Airpak 3 is better than 2. Further, 3 includes alot of package for FSI
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I want to design air-conditioning Systems (Such as: Refrigerator, air-con or any other system
Hakim
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Refrigeration and Air-Conditioning Cloud eTools Available at www.RefrigLab.com
www.RefrigLab.com provides Cloud eTools for refrigeration and air-conditioning components sizing and units tuning for technicians, engineers, and new product developers. The latest release is the Sizing series with 10 eTools.
Natural, HFO and conventional (R290, R600a, R717, R1234yf, R1234ze, R410a, R32, R407c, R134a, R404a, etc.), 41 refrigerants in total, are included for choice with each eTool.
Smart phone or laptop computer can be used to access the website, www.refriglab.com, anywhere with internet accessible.
All of the eTools running for computing and data processing are operated and completed on the Cloud Platform so would not consume the eTool user's mobile data or computer's memory.
1) [UnitqS] for sizing each component's capacity
2) [CompS] for compressor sizing
3) [CapS] for capillary (CAP) tube sizing
4) [SLHX] for suction line heat exchanger sizing
5) [CondS] for condenser air coil sizing
6) [EvapS] for evaporator air coil sizing
7) [CondEvapCS_CapAcc] for sizing condenser and evaporator air coils combined with capillary tube and accumulator
8) [CondEvapCS_SlhxAcc] for sizing condenser and evaporator air coils combined with SLHX and accumulator
9) [CircS] for estimating condenser or evaporator coil circuiting number/passes
10)[Acc3pS] for sizing suction line accumulator using 3 parameters
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I want to improve the cooling perfomance for the cars, what are the improvements to be done in HVAC as well as cabin?
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Dear Yalla,
By changing the air filter and ensuring 100% sealing of the cabin may improve the cooling effect.
Please find the following articles. It may help you.
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Generally pre-heating, humidification , re-heat used in Winter A/C. Whereas cooling coils in Summer A/C i.e. a single de-humidification process
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This is because winter air-conditioning demands heating and humidification.
Dr DB JANI
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We are trying to estimate the power required by HVAC to obtain a desired temperature which we also forecasted based on historical data of occupant behavior and environmental parameters. Is there any theoretical equation that we can use to estimate the HVAC energy to obtain a desired temperature using the historical data of the outdoor temperature and the indoor temperature of the zone .
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As Michalis wrote, you need the history of HVAC delivered or used power together with the history of indoor and outdoor temperature. In addition, if the building is not well protected from the solar radiation, you also need the history of solar radiation. You may then calibrate a simple model such as the one proposed by Michalis or a simple dynamic model including internal capacitace(s). Such a dynamic model is proposed in the old standard EN-ISO 13790 or more recent ISO 52017-1.
No serious prediction can be made on the history of internal and external temperature only.
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Can anyone be kind enough to provide simple comparison of HVAC vs HVDC transmission system simulation in MATLAB/Simulink?
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Dear Affan,
You can find several examples for HVDC systems with relevant models in the Simscape Power Systems Examples of Matlab 2017. The directory to follow is listed below with a fig attached as reference.
Matlab>Simulink>Simscape>Power Systems>Specialized Technology>Facts>
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Manufacturers use capillary tubes for upper cooling by changing the diameter and length of the capillary tube. But I don't know the good diameter and length of the capillary tube for an air conditioner with 500w cooling capacity!
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With CapS/e-Tool at www.refriglab.com, CAP tube contacting factor=0 for detached/separate, =1 for common winding on, =2 for tube-in-tube arrangement with suction line pipe. Contacting Factor varies from 0 to 1.5 for winding on suction line to stand for different contacting degree.
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I have been working on developing a computer model which can be used to simulate the retrofitting measures, in term of adding insulation to the external walls and replacing the low quality windows with a better ones. In addition, the model can be used to simulate a PV system with and without battery.
The videos below show some introduction to my tool. It would be great if you can send me your feedback.
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Hello Mohamed,
I am working on make it available online. once it is ready I can contact you again.
Best,
Mohamad
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the chiller efficiency calculate based on cop=Qc/w
Which equipment will take in W input ?
1-electric motor for compressor
2-condenser pump
3-evaporator pump
4-tower fans
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The best answer can be found in the product selection data for certain chiller "see attached file ".
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