Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.948362
F. Wang, Meng-Chieh Lee, Tong-Bou Chang, Yongsheng Chen, Ron-Chin Jung
Indoor air quality and thermal comfort affects working performance and efficiency, particularly for those who work in the office for prolonged periods. Poor air quality even compromises human health of the staff in the office. For the air-conditioning system using a package-type or split-type air conditioner, introducing fresh air will improve the indoor air quality of the office and affect the perception of thermal comfort. However, it will increase the energy consumption of the air-conditioning system, especially in a hot and humid climate. Attempting to improve indoor air quality and thermal comfort with less power consumption, this study conducts the case study of a total heat exchanger retrofitted in an office building in the hot and humid climate of Taiwan. Field measurement of indoor temperature, humidity, CO2 concentration, and energy consumption, along with thermal sensation votes of staff in the office, have been compared comprehensively after installing the total heat exchanger. Results indicated that the CO2 concentration decreases and thermal comfort evaluation improves satisfactorily after installation of total heat exchanger, even though power consumption increased slightly. It reveals that it is feasible to improve indoor air quality and thermal comfort effectively with less power consumption in the office specifically for the air-conditioning system using a package-type or split-type air conditioner under hot and humid weather conditions.
{"title":"Improving indoor air quality and thermal comfort by total heat exchanger for an office building in hot and humid climate","authors":"F. Wang, Meng-Chieh Lee, Tong-Bou Chang, Yongsheng Chen, Ron-Chin Jung","doi":"10.1080/10789669.2014.948362","DOIUrl":"https://doi.org/10.1080/10789669.2014.948362","url":null,"abstract":"Indoor air quality and thermal comfort affects working performance and efficiency, particularly for those who work in the office for prolonged periods. Poor air quality even compromises human health of the staff in the office. For the air-conditioning system using a package-type or split-type air conditioner, introducing fresh air will improve the indoor air quality of the office and affect the perception of thermal comfort. However, it will increase the energy consumption of the air-conditioning system, especially in a hot and humid climate. Attempting to improve indoor air quality and thermal comfort with less power consumption, this study conducts the case study of a total heat exchanger retrofitted in an office building in the hot and humid climate of Taiwan. Field measurement of indoor temperature, humidity, CO2 concentration, and energy consumption, along with thermal sensation votes of staff in the office, have been compared comprehensively after installing the total heat exchanger. Results indicated that the CO2 concentration decreases and thermal comfort evaluation improves satisfactorily after installation of total heat exchanger, even though power consumption increased slightly. It reveals that it is feasible to improve indoor air quality and thermal comfort effectively with less power consumption in the office specifically for the air-conditioning system using a package-type or split-type air conditioner under hot and humid weather conditions.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"46 1","pages":"731 - 737"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82170388","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.939553
Ali Salim Shirazi, M. Bernier
This article reports on the design and construction of a small-scale laboratory tank to study transient heat transfer in innovative ground heat exchangers designs. The tank is 1.35 m high and has a diameter of 1.4 m. It is filled with well-characterized laboratory-grade sand and instrumented with precisely positioned thermocouples. Experimental results for a 73-h heat injection period followed by a 5-day recovery period for a single U-tube borehole are reported. A comparison is performed against results obtained with an axisymmetric numerical model of the ground surrounding the borehole. It is shown that the agreement between both set of results is very good indicating that accurate experimental data can be obtained with the apparatus.
{"title":"A small-scale experimental apparatus to study heat transfer in the vicinity of geothermal boreholes","authors":"Ali Salim Shirazi, M. Bernier","doi":"10.1080/10789669.2014.939553","DOIUrl":"https://doi.org/10.1080/10789669.2014.939553","url":null,"abstract":"This article reports on the design and construction of a small-scale laboratory tank to study transient heat transfer in innovative ground heat exchangers designs. The tank is 1.35 m high and has a diameter of 1.4 m. It is filled with well-characterized laboratory-grade sand and instrumented with precisely positioned thermocouples. Experimental results for a 73-h heat injection period followed by a 5-day recovery period for a single U-tube borehole are reported. A comparison is performed against results obtained with an axisymmetric numerical model of the ground surrounding the borehole. It is shown that the agreement between both set of results is very good indicating that accurate experimental data can be obtained with the apparatus.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"41 1","pages":"819 - 827"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88577903","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.945852
Y. Diao, Ji Zhang, W. Yu, Yaohua Zhao
A plate heat pipe heat exchanger for use in a room ventilation system to cool or heat outdoor fresh air was designed in this study. One fresh air duct and one exhaust air duct were joined with the heat pipe heat exchanger to study the thermal performance of the thermal recovery system. A ratio of 1 for air volume flow rate between fresh and exhaust air was used to investigate the heat recovery effectiveness and the change in fresh air temperature. The fresh air temperature in the inlet duct was controlled in the range of 27 to 40°C under summer simulation conditions and in the range of 2 to 15°C under winter simulation conditions, whereas the temperature of exhaust air was controlled at approximately 24 and 18 C to simulate summer and winter conditions, respectively. The experimental results show that the temperature variations of fresh and exhaust air increase with increasing inlet fresh air temperature under summer conditions but decrease with increasing inlet temperature of fresh air under winter conditions. The maximum heat recovery effectiveness of the plate heat pipe heat exchanger was 58% in summer and 62% in winter. The change in effectiveness is moderate with different vacuum levels. At a vacuum of 1 × 10−3 Pa, the maximum effectiveness occurred when the filling ratio was 1:3. The experimental results showed that the heat pipe heat exchanger gained a high efficiency of heat recovery with low flow resistance. The energy conservation effect of this heat-pipe heat exchanger was evident.
{"title":"Experimental study on the heat recovery characteristic of a plate heat pipe heat exchanger in room ventilation","authors":"Y. Diao, Ji Zhang, W. Yu, Yaohua Zhao","doi":"10.1080/10789669.2014.945852","DOIUrl":"https://doi.org/10.1080/10789669.2014.945852","url":null,"abstract":"A plate heat pipe heat exchanger for use in a room ventilation system to cool or heat outdoor fresh air was designed in this study. One fresh air duct and one exhaust air duct were joined with the heat pipe heat exchanger to study the thermal performance of the thermal recovery system. A ratio of 1 for air volume flow rate between fresh and exhaust air was used to investigate the heat recovery effectiveness and the change in fresh air temperature. The fresh air temperature in the inlet duct was controlled in the range of 27 to 40°C under summer simulation conditions and in the range of 2 to 15°C under winter simulation conditions, whereas the temperature of exhaust air was controlled at approximately 24 and 18 C to simulate summer and winter conditions, respectively. The experimental results show that the temperature variations of fresh and exhaust air increase with increasing inlet fresh air temperature under summer conditions but decrease with increasing inlet temperature of fresh air under winter conditions. The maximum heat recovery effectiveness of the plate heat pipe heat exchanger was 58% in summer and 62% in winter. The change in effectiveness is moderate with different vacuum levels. At a vacuum of 1 × 10−3 Pa, the maximum effectiveness occurred when the filling ratio was 1:3. The experimental results showed that the heat pipe heat exchanger gained a high efficiency of heat recovery with low flow resistance. The energy conservation effect of this heat-pipe heat exchanger was evident.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"828 - 835"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"86819254","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.954948
J. Srebric
Passive cooling strategies, such as nighttime cooling or winddriven ventilation, provide opportunities for building energy savings, if the mechanical system operation is appropriately integrated with the building architecture. The articles in this section provide successful examples of such integration in several different locations with hot climatic conditions. Additionally, the building-occupant-preferred thermal conditions allow for increased indoor temperature settings. When all of these strategies of mechanical and architectural design are combined with the understanding of occupant preferences, the buildings in hot climates can be much more energy efficient. This section also offers insights into a couple of technological advancements for the chillers, including fault detection/diagnostics and fin design. Finally, a group of articles addresses particle deposition, its sources, and its influence on aircraft cabin design. These studies address the risk reduction of a potential airborne microbe transmission that could promote the spread of communicable diseases. Overall, the integration of different indoor space layouts and mechanical system performance can be addressed as an optimization problem with specific objective functions for the desired system performance. This optimization can be done numerically or experimentally for specific case studies as presented in the articles of this section.
{"title":"First International Conference on Energy and Indoor Environment for Hot Climates","authors":"J. Srebric","doi":"10.1080/10789669.2014.954948","DOIUrl":"https://doi.org/10.1080/10789669.2014.954948","url":null,"abstract":"Passive cooling strategies, such as nighttime cooling or winddriven ventilation, provide opportunities for building energy savings, if the mechanical system operation is appropriately integrated with the building architecture. The articles in this section provide successful examples of such integration in several different locations with hot climatic conditions. Additionally, the building-occupant-preferred thermal conditions allow for increased indoor temperature settings. When all of these strategies of mechanical and architectural design are combined with the understanding of occupant preferences, the buildings in hot climates can be much more energy efficient. This section also offers insights into a couple of technological advancements for the chillers, including fault detection/diagnostics and fin design. Finally, a group of articles addresses particle deposition, its sources, and its influence on aircraft cabin design. These studies address the risk reduction of a potential airborne microbe transmission that could promote the spread of communicable diseases. Overall, the integration of different indoor space layouts and mechanical system performance can be addressed as an optimization problem with specific objective functions for the desired system performance. This optimization can be done numerically or experimentally for specific case studies as presented in the articles of this section.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"25 1","pages":"721 - 721"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89149625","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.950922
Garrett W. Mann, S. Eckels, Byron W. Jones
Engine oil migrating into the bleed air stream of aircraft environmental control systems occurs with enough frequency and deleterious effects to generate significant public interest. While previous work has explored the chemical makeup of the contaminants in the aircraft cabin during these events, little is known about the characteristics of the aerosol resulting from oil contamination of bleed air. This article presents particle counter data (giving both size distributions and concentration information) of the oil droplets from simulated jet engine bleed air. Four particle counters—a scanning mobility analyzer, an aerodynamic particle-sizer, an optical particle counter, and a water-based condensation particle counter—were used in the study encompassing a size range from 13 nm to 20 μm. The aerosol characterization is given for different bleed air temperatures and pressures. The data show a substantial increase of ultrafine particles as the temperature is increased to the maximum temperatures expected during normal aircraft operation. This increase in ultrafine particles is consistent with smoke generated from the oil. The pressure of the bleed air had little discernible effect on the particle size and concentration.
{"title":"Analysis of particulate size distribution and concentrations from simulated jet engine bleed air incidents","authors":"Garrett W. Mann, S. Eckels, Byron W. Jones","doi":"10.1080/10789669.2014.950922","DOIUrl":"https://doi.org/10.1080/10789669.2014.950922","url":null,"abstract":"Engine oil migrating into the bleed air stream of aircraft environmental control systems occurs with enough frequency and deleterious effects to generate significant public interest. While previous work has explored the chemical makeup of the contaminants in the aircraft cabin during these events, little is known about the characteristics of the aerosol resulting from oil contamination of bleed air. This article presents particle counter data (giving both size distributions and concentration information) of the oil droplets from simulated jet engine bleed air. Four particle counters—a scanning mobility analyzer, an aerodynamic particle-sizer, an optical particle counter, and a water-based condensation particle counter—were used in the study encompassing a size range from 13 nm to 20 μm. The aerosol characterization is given for different bleed air temperatures and pressures. The data show a substantial increase of ultrafine particles as the temperature is increased to the maximum temperatures expected during normal aircraft operation. This increase in ultrafine particles is consistent with smoke generated from the oil. The pressure of the bleed air had little discernible effect on the particle size and concentration.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"20 1","pages":"780 - 789"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83684845","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.953872
Jamal Alabid, A. Taki
This article assesses the most common architectural and environmental strategies in Ghadames housing in Libya. Preliminary data were collected through field surveys undertaken in July 2013, the hottest and driest season in Ghadames. The surveys investigated the indoor thermal environment and efficiency of energy use in Ghadames housing. The actual mean vote scale was used to investigate occupants’ thermal feeling coupled with recording physical environment and also actual measurements of a number of existing houses. Additionally, objective surveys were conducted to (a) verify the subjective data, (b) provide an overall view of the residents’ life style in the old town, and (c) understand the most significant techniques employed in old dwellings. The subjective survey “questionnaire” distributed among nine new and eight old houses shows that the majority of respondents is satisfied with the number of architectural issues in modern housing design. This general satisfaction excludes the inherited identity of the traditional architecture embedded within the society. On the other hand, occupants are more satisfied with old buildings in regard to indoor environmental conditions, energy consumption, and construction materials. The occupants of old houses expressed their thermal satisfaction with the indoor comfort conditions, but the predicted mean vote, based on measurements and ISO 7730, implied discomfort (hot).The survey also carried out interviews with a number of locals, underlining their personal impressions and preference toward the change of the existing built environment. Findings indicate that, occupants’ satisfaction and perception toward the built environment have not been achieved in new housing developments of Ghadames owing to the lack of understanding of the sociocultural needs of the local community. In addition, a 3D digital model was created for the old town and imparted a full understanding of the building dynamics and physics, explicating the complexity of the compactness of its urban morphologies. The results also showed subjects were feeling neutral to slightly warm in old buildings even when indoor air temperatures reached 32°C.
{"title":"Bioclimatic housing design to desert architecture: A case study of Ghadames, Libya","authors":"Jamal Alabid, A. Taki","doi":"10.1080/10789669.2014.953872","DOIUrl":"https://doi.org/10.1080/10789669.2014.953872","url":null,"abstract":"This article assesses the most common architectural and environmental strategies in Ghadames housing in Libya. Preliminary data were collected through field surveys undertaken in July 2013, the hottest and driest season in Ghadames. The surveys investigated the indoor thermal environment and efficiency of energy use in Ghadames housing. The actual mean vote scale was used to investigate occupants’ thermal feeling coupled with recording physical environment and also actual measurements of a number of existing houses. Additionally, objective surveys were conducted to (a) verify the subjective data, (b) provide an overall view of the residents’ life style in the old town, and (c) understand the most significant techniques employed in old dwellings. The subjective survey “questionnaire” distributed among nine new and eight old houses shows that the majority of respondents is satisfied with the number of architectural issues in modern housing design. This general satisfaction excludes the inherited identity of the traditional architecture embedded within the society. On the other hand, occupants are more satisfied with old buildings in regard to indoor environmental conditions, energy consumption, and construction materials. The occupants of old houses expressed their thermal satisfaction with the indoor comfort conditions, but the predicted mean vote, based on measurements and ISO 7730, implied discomfort (hot).The survey also carried out interviews with a number of locals, underlining their personal impressions and preference toward the change of the existing built environment. Findings indicate that, occupants’ satisfaction and perception toward the built environment have not been achieved in new housing developments of Ghadames owing to the lack of understanding of the sociocultural needs of the local community. In addition, a 3D digital model was created for the old town and imparted a full understanding of the building dynamics and physics, explicating the complexity of the compactness of its urban morphologies. The results also showed subjects were feeling neutral to slightly warm in old buildings even when indoor air temperatures reached 32°C.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"4 1","pages":"760 - 769"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"75316301","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.950895
T. Zhang, X. You
An inverse design method is proposed to achieve the pre-set control objectives of the aircraft cabin environment. The method combines the artificial neural network and the genetic algorithm, and the training and testing data of the artificial neural network is obtained by computational fluid dynamics analysis. Both of the thermal comfort and energy consumption are considered in the inverse design. The artificial neural network is used to identify the relationship between the thermal comfort and the air supply parameters (inlet velocity magnitude and angle, inlet air temperature). The genetic algorithm coupled with the well-trained artificial neural network is used to design the aircraft cabin environment. Numerical results show that the Bayesian regularization algorithm is proved to have better generalization capability than the other training algorithms for the artificial neural network. The increase of training data quantity improves the generalization capability of the artificial neural network, while it spends more simulation time. A computational fluid dynamics database with 60 datasets is shown to be suitable to the present inverse design, and the testing error of the artificial neural network is below 8.2%. Several groups of optimal air supply parameters are found with different trade-offs between the thermal comfort and energy consumption. The best solution of thermal comfort, i.e., the percentage of zone with |PMV| >0.5 in all cabin control domains, is less than 7.8%.
{"title":"Inverse design of aircraft cabin environment by coupling artificial neural network and genetic algorithm","authors":"T. Zhang, X. You","doi":"10.1080/10789669.2014.950895","DOIUrl":"https://doi.org/10.1080/10789669.2014.950895","url":null,"abstract":"An inverse design method is proposed to achieve the pre-set control objectives of the aircraft cabin environment. The method combines the artificial neural network and the genetic algorithm, and the training and testing data of the artificial neural network is obtained by computational fluid dynamics analysis. Both of the thermal comfort and energy consumption are considered in the inverse design. The artificial neural network is used to identify the relationship between the thermal comfort and the air supply parameters (inlet velocity magnitude and angle, inlet air temperature). The genetic algorithm coupled with the well-trained artificial neural network is used to design the aircraft cabin environment. Numerical results show that the Bayesian regularization algorithm is proved to have better generalization capability than the other training algorithms for the artificial neural network. The increase of training data quantity improves the generalization capability of the artificial neural network, while it spends more simulation time. A computational fluid dynamics database with 60 datasets is shown to be suitable to the present inverse design, and the testing error of the artificial neural network is below 8.2%. Several groups of optimal air supply parameters are found with different trade-offs between the thermal comfort and energy consumption. The best solution of thermal comfort, i.e., the percentage of zone with |PMV| >0.5 in all cabin control domains, is less than 7.8%.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"77 1","pages":"836 - 843"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83876603","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.953845
Noor Hanita Abdul Majid, Nozomi Takagi, S. Hokoi, S. Ekasiwi, Tomoko Uno
In conventional air-conditioning design, the comfortable range of temperatures is between 25°C and 27°C with relative humidity levels of 40% to 60%; these numbers vary only slightly based on a person's race and country. Several studies in tropical climates show that the observed thermal comfort requirement often does not agree with those obtained based on experiments, which have mainly used North American subjects. However, there is no consistent rationale that explains why comfort requirements are different in hot climates, suggesting that more surveys on thermal comfort may be needed in the tropics. In Asia, there has recently been a rapid and widespread diffusion of air conditioners; therefore, a survey was conducted to clarify what temperature and humidity level people in Asian countries prefer in order to feel comfortable. Following that research, this article presents the results of a questionnaire survey on the use of air conditioners in houses in hot, dry climates. Nizwa and Rustak, Oman, characterized by the hot, arid climate of the Arabian Peninsula, were chosen as survey areas. The questionnaire survey was distributed to students of Nizwa University. Questions were asked about the duration of air-conditioner use and preferred air-conditioner temperature settings. To determine how respondents felt about their indoor environment, questions were also asked about the thermal sensations that were experienced while using the air conditioner. In both cities, the mean operating time of the air conditioner was very long. The respondents reported selecting a low temperature setting while sleeping, despite the fact that many of them reported that they were cold while sleeping. Ninety percent of respondents reported a cold, cool, or neutral thermal sensation while using the air conditioner without feeling discomfort.
{"title":"Field survey of air conditioner temperature settings in a hot, dry climate (Oman)","authors":"Noor Hanita Abdul Majid, Nozomi Takagi, S. Hokoi, S. Ekasiwi, Tomoko Uno","doi":"10.1080/10789669.2014.953845","DOIUrl":"https://doi.org/10.1080/10789669.2014.953845","url":null,"abstract":"In conventional air-conditioning design, the comfortable range of temperatures is between 25°C and 27°C with relative humidity levels of 40% to 60%; these numbers vary only slightly based on a person's race and country. Several studies in tropical climates show that the observed thermal comfort requirement often does not agree with those obtained based on experiments, which have mainly used North American subjects. However, there is no consistent rationale that explains why comfort requirements are different in hot climates, suggesting that more surveys on thermal comfort may be needed in the tropics. In Asia, there has recently been a rapid and widespread diffusion of air conditioners; therefore, a survey was conducted to clarify what temperature and humidity level people in Asian countries prefer in order to feel comfortable. Following that research, this article presents the results of a questionnaire survey on the use of air conditioners in houses in hot, dry climates. Nizwa and Rustak, Oman, characterized by the hot, arid climate of the Arabian Peninsula, were chosen as survey areas. The questionnaire survey was distributed to students of Nizwa University. Questions were asked about the duration of air-conditioner use and preferred air-conditioner temperature settings. To determine how respondents felt about their indoor environment, questions were also asked about the thermal sensations that were experienced while using the air conditioner. In both cities, the mean operating time of the air conditioner was very long. The respondents reported selecting a low temperature setting while sleeping, despite the fact that many of them reported that they were cold while sleeping. Ninety percent of respondents reported a cold, cool, or neutral thermal sensation while using the air conditioner without feeling discomfort.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"751 - 759"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74773750","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.952976
H. Chaudhry, B. Hughes
The passive airside cooling capability of heat pipes operating under high-temperature natural ventilation airstreams was investigated in this study. Pure water was used as the internal working fluid to ensure the system remained sustainable in its operation. The physical domain included 19 cylindrical copper heat pipes assembled in a systematic vertical arrangement. Using the monthly temperature data of Doha, Qatar, as a case-study reference, the efficiency of the heat pipe model was analyzed at fixed inlet air velocities of 1 and 2.3 m/s. At a source temperature of 314 K, the results showed a maximum temperature reduction of 3.8 K for an external air velocity of 1 m/s. A cooling load of 976 W was achieved, indicating a heat pipe effectiveness of 6.4% when the velocity was increased to 2.3 m/s. Wind tunnel experimental testing was conducted to validate the findings. A good correlation was observed between the two techniques with error variations of 10% for velocity and 28% for temperature. The present work identified the potential of sustainable pre-cooling using heat pipes in natural ventilation airstreams for regions with hot and dry climatic conditions. The concept is currently under intellectual property protection (GB1321709.6).
{"title":"Passive pre-cooling potential for reducing building air-conditioning loads in hot climates","authors":"H. Chaudhry, B. Hughes","doi":"10.1080/10789669.2014.952976","DOIUrl":"https://doi.org/10.1080/10789669.2014.952976","url":null,"abstract":"The passive airside cooling capability of heat pipes operating under high-temperature natural ventilation airstreams was investigated in this study. Pure water was used as the internal working fluid to ensure the system remained sustainable in its operation. The physical domain included 19 cylindrical copper heat pipes assembled in a systematic vertical arrangement. Using the monthly temperature data of Doha, Qatar, as a case-study reference, the efficiency of the heat pipe model was analyzed at fixed inlet air velocities of 1 and 2.3 m/s. At a source temperature of 314 K, the results showed a maximum temperature reduction of 3.8 K for an external air velocity of 1 m/s. A cooling load of 976 W was achieved, indicating a heat pipe effectiveness of 6.4% when the velocity was increased to 2.3 m/s. Wind tunnel experimental testing was conducted to validate the findings. A good correlation was observed between the two techniques with error variations of 10% for velocity and 28% for temperature. The present work identified the potential of sustainable pre-cooling using heat pipes in natural ventilation airstreams for regions with hot and dry climatic conditions. The concept is currently under intellectual property protection (GB1321709.6).","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"738 - 750"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"89982673","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2014-10-03DOI: 10.1080/10789669.2014.936796
Haitao Hu, Jingdan Gao, G. Ding, Yi-feng Gao, J. Song
The application of fin-and-tube heat exchangers with small diameter microgroove tubes in room air conditioners has rapidly increased recently, and fins suitable for such heat exchangers should be developed. In the present study, a louver fin suitable for the evaporator with small diameter microgroove tubes was designed by applying computational fluid dynamics method, and the performance of the optimized and existing louver fins were experimentally investigated. Experimental results show that water bridge occurs at the bottom of the optimized fins for small diameter tubes, which is not the same as that for larger diameter tubes; for the fins of the evaporator with small diameter tubes, the increase of the fin pitch leads to the decrease of Colburn j factors. Based on the experimental data, a correlation of the Colburn j factor was developed to predict the heat transfer rate of the evaporator with small diameter microgroove tubes, and agrees with 85% of the experimental data within a deviation of ±20%.
{"title":"Fin design for an evaporator with small diameter microgroove tubes","authors":"Haitao Hu, Jingdan Gao, G. Ding, Yi-feng Gao, J. Song","doi":"10.1080/10789669.2014.936796","DOIUrl":"https://doi.org/10.1080/10789669.2014.936796","url":null,"abstract":"The application of fin-and-tube heat exchangers with small diameter microgroove tubes in room air conditioners has rapidly increased recently, and fins suitable for such heat exchangers should be developed. In the present study, a louver fin suitable for the evaporator with small diameter microgroove tubes was designed by applying computational fluid dynamics method, and the performance of the optimized and existing louver fins were experimentally investigated. Experimental results show that water bridge occurs at the bottom of the optimized fins for small diameter tubes, which is not the same as that for larger diameter tubes; for the fins of the evaporator with small diameter tubes, the increase of the fin pitch leads to the decrease of Colburn j factors. Based on the experimental data, a correlation of the Colburn j factor was developed to predict the heat transfer rate of the evaporator with small diameter microgroove tubes, and agrees with 85% of the experimental data within a deviation of ±20%.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"91 1","pages":"790 - 797"},"PeriodicalIF":0.0,"publicationDate":"2014-10-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80519934","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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