Performance Improvement of Condensation Reduction and Removal in Heat Recovery Ventilators Using Purge Methods

In this study, several purge and ventilation methods are proposed to reduce and remove condensation in a heat recovery ventilator for commercial and household buildings. The effects of the airflow rate, duration of ventilation, purge interval, and return air temperature on the quantities of condensation and condensation removal in the heat recovery ventilator are analyzed. The increase in the air flow rate and return air temperature increases the condensation removal rate owing to the enhanced evaporation of the condensate. Furthermore, the reductions in the duration of ventilation and purge interval decreased the accumulation of condensate on the heat exchanger element. Based on the experimental results, optimum ventilation and purge strategies are proposed according to the outdoor temperature. The operation of the heat recovery ventilator with the proposed ventilation and purge strategies shows at least a 33% and up to an 80% reduction in the quantity of condensate compared with a given operation method. Accordingly, the proposed operation strategies can significantly reduce the growth of microorganisms and fungi and also increase the efficiency of a heat recovery ventilator. However, further investigation on the detailed performance according to the outdoor humidity and overall energy analysis is necessary to supplement the limitations of this study.

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EFFECT OF CONDENSATION ON THE EFFICIENCY OF HEAT RECOVERY VENTILATORS FOR BROILER HOUSES

International Journal of Air-Conditioning and Refrigeration ◽

10.1142/s2010132513500090 ◽

2013 ◽

Vol 21 (02) ◽

pp. 1350009 ◽

Cited By ~ 3

Author(s):

HWATAIK HAN ◽

SANG-HOON NAM ◽

GEON-SOO HAN

Keyword(s):

Heat Exchanger ◽

Relative Humidity ◽

Latent Heat ◽

Heat Recovery ◽

Harsh Environments ◽

Sensible Heat ◽

Outdoor Temperature ◽

Toxic Gases ◽

Temperature Efficiency ◽

Plate Type

This study experimentally investigates the effect of internal condensation on the performance of a heat recovery ventilator. Experiments were performed using a plate-type sensible heat exchanger element that was designed for very humid and dusty environments such as chicken broiler houses. The results of these experiments show that the temperature efficiency considering condensation is always greater than that without considering latent heat. As outdoor temperature decreases or indoor relative humidity increases, temperature efficiency increases owing to an increase in the rate of condensation. The present polypropylene-based sensible heat exchanger element could be a solution for harsh environments because it can discharge condensate water by gravity and is resistant to moisture and other toxic gases.

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Experimental Analysis of an Air-to-Air Heat Exchanger for Use in a Refrigeration Brayton Cycle

Volume 3 ◽

10.1115/ht-fed2004-56544 ◽

2004 ◽

Author(s):

Alireza Kargar ◽

Mohammad H. Hosni ◽

Steve Eckels ◽

Tomas Gielda

Keyword(s):

Heat Exchanger ◽

Pressure Drop ◽

Removal Rate ◽

Experimental Results ◽

Airflow Rate ◽

Brayton Cycle ◽

Moisture Removal ◽

Research Project ◽

Cycle System ◽

Automotive Air Conditioning

The refrigeration Brayton cycle, which has been used extensively in various industries, has an excellent potential for use in automotive air conditioning applications. However, the air-cycle system has a couple of drawbacks including fog generation and low cycle efficiency. In this research project, an air-to-air heat exchanger called a ‘mixer’ is designed and used at the outlet of a refrigeration Brayton cycle. The primary function of the mixer is to remove moisture from the secondary warm airflow into the system. Successful moisture removal from the secondary airflow results in achieving the second function of fog dissipation from the primary cold airflow. In order for the system to perform appropriately, the moisture removal rate must be kept at the highest possible rate. The experimental results from this research project reveal that to enhance moisture removal rate, one may either increase the primary cold airflow rate, decrease the secondary warm airflow rate, or the combination of the above airflow adjustments. Furthermore, based on experimental results, one may speculate that there is an optimum point in decreasing the secondary airflow rate. However, in increasing the primary airflow rate, one must be aware of the pressure drop through the cold side of the mixer as the higher pressure drop results in higher power consumption for the Brayton cycle. It is important to point out that appropriate levels of the primary and secondary airflows impacts the mixer effectiveness, and that for a constant cold airflow rate, decreasing the warm airflow rate below the cold airflow rate results in higher effectiveness.

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The influence of airflow on the effectiveness of rotary heat exchangers operating under high-speed rotor conditions

E3S Web of Conferences ◽

10.1051/e3sconf/201911600032 ◽

2019 ◽

Vol 116 ◽

pp. 00032

Author(s):

Paulina Kanaś ◽

Andrzej Jedlikowski ◽

Sergey Anisimov ◽

Borys Vager

Keyword(s):

Mass Transfer ◽

Heat Exchanger ◽

Heat And Mass Transfer ◽

Heat Exchangers ◽

Heat Recovery ◽

High Speed ◽

Airflow Rate ◽

Sharp Drop ◽

Transfer Processes ◽

Mass Transfer Processes

The paper presents an analysis of heat and mass transfer processes occurring inside the rotary heat exchanger operating under high-speed rotor conditions for different values of the airflow rate. For this purpose the original mathematical α-model was used. Conducted computer simulations allowed to determine the influence of Number of Transfer Units (NTU) of airflow on the temperature effectiveness as well as on the distribution of different active heat and mass transfer zones: “dry”, “wet” and “frost”. It was found that the increase of the values of NTU strictly affects the increase of the effectiveness of heat recovery. Another issue emerging from this study is the fact that in the certain range of low values of NTU there is no “dry” area created. It was established that at low values of NTU (NTU≈1) “frost” area extremum and sharp drop in the “frost” area accumulation are observed.

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Study on Thermal Performance of a New Solar Air Heating Collector

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.706-708.1814 ◽

2013 ◽

Vol 706-708 ◽

pp. 1814-1817

Author(s):

Zhi Zhuang ◽

Jing Xue ◽

Hai Ye

Keyword(s):

Aspect Ratio ◽

Air Temperature ◽

Thermal Performance ◽

Thermal Efficiency ◽

Macroscopic Model ◽

Airflow Rate ◽

Effective Energy ◽

Air Flow Rate ◽

Air Heating ◽

Solar Air Collector

The thermal performance of a new Solar air Collector with Colored Fins (SCCF) used for heating was studied. A macroscopic model was proposed based on the law of mass and energy conservation. The effects of the parameters such as dimensions of SCCF, fin angle and material of the fins on the outlet air temperature, airflow rate, effective energy and thermal efficiency were discussed. The results indicate that thermal performance of SCCF can be obviously improved by the increases of aspect ratio, fin angle and vent size. The air flow rate is the dominated factor affecting effective energy and thermal efficiency of SCCF. All these study can be used for guiding the design of SCCF.

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Experimental Study of Solar Air Heating System Based on Unglazed Transpired Collector

ASME 2011 5th International Conference on Energy Sustainability, Parts A, B, and C ◽

10.1115/es2011-54837 ◽

2011 ◽

Cited By ~ 1

Author(s):

Lixin Gao ◽

Hua Bai ◽

Xiumu Fang

Keyword(s):

Surface Temperature ◽

Air Temperature ◽

Flow Rate ◽

Temperature Rise ◽

Air Flow ◽

Heating System ◽

Airflow Rate ◽

Air Flow Rate ◽

Air Heating ◽

Collector Efficiency

An experimental rig was set up to test the thermal performance of a solar air heating system based on an unglazed transpired collector of 2.5 m2. The experiment was carried out at Harbin Institute of Technology in the city of Harbin, which is located in northeastern China, at latitude 45°41′ N and longitude 126°37′ E. The tests were spread over a number of days, in which the 4-day experimental data within the period were selected as the sample for analysis. Experimental results show that solar collector’s surface temperature and exit air temperature increase with increasing solar irradiation. The influence of ambient temperature on surface temperature and exit temperature is negligible. Temperature rise decreases with increasing air flow rate, while collector efficiency increases with increasing air flow rate. For an air flow rate of 100 m3/h in Test 1, the average air temperature rise and collector efficiency were 28.86°C and 72% respectively; for an air flow rate of 235 m3/h in Test 2, the average air temperature rise and collector efficiency were 11.52°C and 78% respectively. Higher airflow rate tends to operate the collector at lower surface temperature, which results in lower overall heat losses from the collector to the surroundings, therefore increasing airflow rate reduces air temperature rise and enhances the collector efficiency. The average efficiency of the experimental solar air heating system in the 4-day experiment period was 72%, 78%, 61%, and 72% respectively, which are higher than most conventional glazed flat-plate solar air collectors. With better coordination with architectural design at early stage in a project, this building-integrated solar air heating system can be both aesthetically and technically viable.

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Air purification in industrial plants producing automotive rubber components in terms of energy efficiency

Open Engineering ◽

10.1515/eng-2017-0015 ◽

2017 ◽

Vol 7 (1) ◽

pp. 106-114 ◽

Cited By ~ 2

Author(s):

Andrzej Grzebielec ◽

Artur Rusowicz ◽

Adam Szelągowski

Keyword(s):

Energy Efficiency ◽

Heat Exchanger ◽

Economic Analysis ◽

Power Consumption ◽

Air Temperature ◽

Heat Recovery ◽

Waste Heat ◽

Hot Water ◽

Air Purification ◽

Cost Efficient

AbstractIn automotive industry plants, which use injection molding machines for rubber processing, tar contaminates air to such an extent that air fails to enter standard heat recovery systems. Accumulated tar clogs ventilation heat recovery exchangers in just a few days. In the plant in which the research was conducted, tar contamination causes blockage of ventilation ducts. The effect of this phenomenon was that every half year channels had to be replaced with new ones, since the economic analysis has shown that cleaning them is not cost-efficient. Air temperature inside such plants is often, even in winter, higher than 30°C. The air, without any means of heat recovery, is discharged outside the buildings. The analyzed plant uses three types of media for production: hot water, cold water at 14°C (produced in a water chiller), and compressed air, generated in a unit with a rated power consumption of 180 kW. The aim of the study is to determine the energy efficiency improvement of this type of manufacturing plant. The main problem to solve is to provide an air purification process so that air can be used in heat recovery devices. The next problem to solve is to recover heat at such a temperature level that it would be possible to produce cold for technological purposes without air purification. Experimental studies have shown that air purification is feasible. By using one microjet head, a total of 75% of tar particles was removed from the air; by using 4 heads, a purification efficiency of 93% was obtained. This method of air purification causes air temperature to decrease from 35°C to 20°C, which significantly reduces the potential for heat recovery. The next step of the research was designing a cassette-plate heat exchanger to exchange heat without air purification. The economic analysis of such a solution revealed that replacing the heat exchanger with a new one even once a year was not cost-efficient. Another issue examined in the context of energy efficiency was the use of waste heat from the air compressor. Before any changes, the heat was picked up by a chilled water system. The idea was to use the heat for cold generation. Temperature of oil and air in the compressor exceeds 65°C, which makes it a perfect heat source for an adsorption refrigeration device. This solution reduced the cooling demand by 147 kW, thus reducing power consumption by 36.75 kW. This study shows that even in factories where air is heavily polluted with tar, there are huge potentials for energy recovery using existing technical solutions. It is important to note that problems of this kind should always be approached individually.

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Performance improvement of supercritical carbon dioxide power cycles through its integration with bottoming heat recovery cycles and advanced heat exchanger design: A review

International Journal of Energy Research ◽

10.1002/er.5319 ◽

2020 ◽

Vol 44 (9) ◽

pp. 7108-7135 ◽

Cited By ~ 7

Author(s):

Ramy H. Mohammed ◽

Ali Sulaiman Alsagri ◽

Xiaolin Wang

Keyword(s):

Carbon Dioxide ◽

Heat Exchanger ◽

Supercritical Carbon Dioxide ◽

Performance Improvement ◽

Heat Recovery ◽

Power Cycles ◽

Heat Exchanger Design ◽

Recovery Cycles ◽

Supercritical Carbon

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Experimental Investigation on the Plate Heat Pipe Heat Exchanger for Heat Recovery Characteristic in Room Ventilation

2010 14th International Heat Transfer Conference, Volume 5 ◽

10.1115/ihtc14-22435 ◽

2010 ◽

Author(s):

Wen-Jing Yu ◽

Yan-Hua Diao ◽

Yao-Hua Zhao

Keyword(s):

Heat Exchanger ◽

Heat Pipe ◽

Double Layer ◽

Air Temperature ◽

Heat Recovery ◽

Single Layer ◽

Working Fluid ◽

Plate Heat ◽

Air Volume ◽

Pipe Heat

A plate HPHE (heat pipe heat exchanger) has been designed and constructed for heat recovery in this paper. The plate HPHE is constituted by plate heat pipes with microchannels. Many parameters affect the performance of the HPHE. In this paper, the effect of three parameters: inlet air temperature (27–40°C), working fluid (methanol, acetone, R113, R141b), and heat exchange area (single layer, double layer) were investigated experimentally. The overall experiments were carried out under the simulated summer condition, the vacuum of the HPHE was set at 1×10−3Pa, and the filling ratio was 1/3. The air volume rates were changed from 60, 90, 120 and 150 m3/h. The fresh air temperature varied from 27 to 40°C, whereas the return air temperature was kept at about 24°C. The results show that, at the same air volume, the effectiveness increases with increase of the inlet temperature of fresh air. The effectiveness of HPHEd with R141b as working fluid is superior to R113, acetone and methanol, and the maximum effectiveness reaches to 58%. The effectiveness of the HPHE of single layer is lower than that of double layer by about 6%–18% at the temperature from 29 to 40°C.

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