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(a) Schematic of Wrap-Around Heat Pipe (WAHP) dehumidifier system. (b) Psychrometric plots of processes through conventional dehumidifier and a WAHP dehumidifier.
Source publication
Although wrap-around heat pipes (WAHP) are widely used for enhanced dehumidification systems in tropical and hot-humid climates, very few literature resources have actually reported any control methodology applicable for WAHP dehumidifier systems for an entire year operation. In the present work, a methodology is proposed for an outdoor air unit eq...
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... to this, refrigerant vapor condenses into liquid and transported back to the evaporator via gravity and the whole cycle is repeated. Fig.1 (a) shows the schematics of a basic WAHP dehumidifier system. WAHP tubes can also be fitted with electrically operated solenoid valves to control its overall effectiveness and reheat temperature by controlling the refrigerant flow through heat pipe system 17 . ...
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... allows dehumidification of air by the coil to the required temperature at a comparatively higher coil apparatus dew point (ADP) temperature and reduces overall coil load and size. Fig.1 (b) shows psychrometric plots of a conventional dehumidifier system and a WAHP dehumidifier system, respectively. In both cases, the dehumidifier coils are assumed to cool and dehumidify air to the same temperature. ...
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... addition, a large number of climatic conditions are clustered in psychrometric regions 3 and 4 in case of wet climate zones that leads to lower utilization ratios in these zones. Fig.10 shows the scatter plots of percentages of cooling plant energy savings against The dehumidifier coil sensibly cools the air down to the required supply dew point followed by reheat through the WAHP condenser. ...
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... percentage deviations in these energies help in understanding and quantifying how different inputs for t band offsets the simulation results as compared to considering design condenser reheat for t band in climatic controls. Fig.11 depicts the variation of annual cooling loads with t band . ...
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... observation is due to the combined effects of increase in dehumidifier loads and decrease in precooling coil loads (for transitioning into controlled zone) with an expansion of WAHP inlet temperature band. However, the deviations of annual cooling energies in both the models primarily vary in a range of ± 8% as shown in Fig.12. The left side in Fig.12 depicts the number of simulation test cases or frequency of test scenarios with results belonging to specific percentage deviation bins. ...
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... the deviations of annual cooling energies in both the models primarily vary in a range of ± 8% as shown in Fig.12. The left side in Fig.12 depicts the number of simulation test cases or frequency of test scenarios with results belonging to specific percentage deviation bins. ...
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... left side in Fig.12 depicts the number of simulation test cases or frequency of test scenarios with results belonging to specific percentage deviation bins. The normality plots on the right hand side in Fig.12 confirms normal distribution of percentage variations of annual chiller energy across 60 simulation scenarios considered for both of the office models. ...
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... or frequency of test scenarios with results belonging to specific percentage deviation bins. The normality plots on the right hand side in Fig.12 confirms normal distribution of percentage variations of annual chiller energy across 60 simulation scenarios considered for both of the office models. On careful observation, it can be concluded from Fig. 12 that deviations in annual cooling energy vary between -7 to +7.4% and -6 to +7.8%, in small and large office models, respectively, at a confidence interval of 95% with the considered t band ...
Citations
... A relative humidity ratio of 48.2-87.4% indicates the ability of air to hold water vapor [23,24]. The amount of water vapor present in the air per unit of dry air was analyzed by reviewing the water vapor content during cooling or heating the air [25,26]. The energy requirement for heating or cooling air was determined by the total energy present per unit mass of dry air [27]. ...
Isolation rooms are crucial in healthcare facilities to prevent the spread of infectious diseases. Infectious diseases can be transmitted to humans from humans or through animals known as zoonoses. With the increase in the number of COVID-19 cases, isolation rooms have become one of the most critical facilities in hospitals. Maintaining the correct temperature and humidity in these isolation rooms is a challenge, considering the heating, ventilation, and air conditioning (HVAC) systems that continuously consume large amounts of energy. With the application of energy conservation methods, the total energy consumption of HVAC systems can be reduced. Many studies have shown that the heat pipe heat exchanger (HPHE) technology can contribute significantly to energy savings using HVAC systems. In this study, the effectiveness of an HPHE on an HVAC system in an isolation room was examined, and the total energy reduction was quantified. The HPHE consisted of two rows with ten heat pipes in each row, arranged in a staggered configuration with fresh air temperature and mass flow variations. The inlet fresh air temperatures varied at 32, 35, 37, and 40 °C and fresh air velocities at 1.2, 1.6, 2.2, and 2.6 m/s. Using a chiller, the inlet fresh air was cooled to a comfortable temperature zone, approximately 24.4–25.2 °C, in the isolation room. Notably, higher velocities decreased the effectiveness of the HPHE. An increase in the flow rate enhanced the system, thereby improving the heat recovery value. The increase in the inlet fresh air temperature from 32 °C, that yielded an energy saving of 1.23 W, to 40 °C, resulted in a further energy saving of 1.85 W. The application of the HPHE in the HVAC system in isolation rooms represents a significant innovation that contributes to a reduction in total energy consumption.
An air-conditioning system (ACS), which consumes large amounts of high-grade energy, is essential for maintaining the indoor thermal environment of modern buildings. However, an ACS consumes almost half of the total energy of the building. Therefore, it is necessary to reduce the energy consumption of the ACS to promote energy conservation and emission reduction in the building sector. In fact, there is an abundance of waste heat and low-grade energies with the potential to be utilized in ACS in nature, but many of them are not utilized efficiently or cannot be utilized at all due to the low efficiency of thermal energy conversion. Known as a passive thermal transfer device, the application of a heat pipe (HP) in the ACS has shown explosive growth in recent years. HPs have been demonstrated to be an effective method for reducing building cooling and heating demands and energy consumption in ACS with experimental and simulation methods. This paper summarizes the different HP types applied in the ACS and provides brief insight into the performance enhancement of the ACS integrated with HP. Four types of HPs, namely tubular HP (THP), loop HP (LHP), pulsating HP (PHP) and flat HP (FHP), are presented. Their working principles and scope of applications are reviewed. Then, HPs used in natural cooling system, split air conditioner (SAC), centralized ACS (CACS) and cooling terminal devices are comprehensively reviewed. Finally, the heat transfer characteristics and energy savings of the above systems are critically analyzed. The results show that the performance of the HP is greatly affected by its own structure, working fluid and external environmental conditions. The energy saving of ACS coupled with HP is 3–40.9%. The payback period of this system ranges from 1.9–10 years. It demonstrates that the HP plays a significant role in reducing ACS energy consumption and improving indoor thermal comfort.
