Heating Ventilation and Air-Conditioning - Science topic

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,

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

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.

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 ?

explain your idea

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 ?

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)

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!!

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

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

Specification for use

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. =)

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

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?

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

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.

explain your idea

It is necessary to react not only with administrative solutions against pandemic situations like the case with Covid 19.

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.

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!

Heating Ventilation Air-conditioning System related thesis topic for thesis

How to write the fuel and product exergy balances in the cascade heat exchanger in the cascade refrigeration system?

Dear fellow friends, are there any good and PRACTICAL references for above subject matter? which can show real life problems and calculations. Thanks

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.

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,

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.

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?

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

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:

2. COOLINGEIRLOWPLR minimum value of X = 0.500 is out of range. It 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.

So, finally, I obtain the fatal error here below (caused by the three warnings above):

Then, EnergyPlus terminates.

Is there anyone who could help me?

PS: If useful, I could attach the IDF.

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 ??????

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.

-

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.

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?

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?

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

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.

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?

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

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.

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.

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.

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

Office type: Open space office/closed office

HVAC system: Yes/No

Natural ventilated NV: Yes/No

Season: Winter/Summer

-3 Cold

+2 Cool

+1 Slightly cool

0 Comfotable, Neutral

+1 Slightly warm

+2 Warm

+3 Hot

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!

This refers to modelling for VAV and HVAC systems

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?

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?

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.

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?

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?

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?

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.

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?

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,

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,

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

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?

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.)

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.

Require for thermal optimization of thermal insulation HVAC application.......

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.

Hi

How can I calculate run fraction (Fc) based on bin method in ground source heat pump?

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

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?

I want to design air-conditioning Systems (Such as: Refrigerator, air-con or any other system

Hakim

I want to improve the cooling perfomance for the cars, what are the improvements to be done in HVAC as well as cabin?

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

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 .

Can anyone be kind enough to provide simple comparison of HVAC vs HVDC transmission system simulation in MATLAB/Simulink?

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!

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.

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