HVAC&R Research最新文献

{"title":"Superheating control using an adaptive PID controller","authors":"A. Maia, Juan C. Horta-Gutierrez, R. Koury, L. Machado","doi":"10.1080/10789669.2013.874842","DOIUrl":"https://doi.org/10.1080/10789669.2013.874842","url":null,"abstract":"Electronic expansion valves have been used to replace conventional expansion devices in many refrigeration systems. Electronically controlled valves respond more rapidly to changes in operating conditions and improve the steady-state superheating. These valves are usually used with an automatic controller that regulates the superheating at the evaporator outlet. The controller gains (Kp, Ti, and Td) must be properly tuned for efficient operation. However, these controllers can result in poor performance because they have been poorly tuned or put into operation using factory tuning. For refrigeration systems that are subject to large changes in operating conditions, the controller gains should be adjusted for each change to improve the system performance. Within this context, we developed an adaptive Proportional-Integral-Derivative controller (PID controller) in this study to regulate the degree of superheating. A dynamic model obtained from experimental tests was used in the controller design. The controller effectiveness was evaluated using computer simulations and experimental tests. In comparison to a nonadaptive PID controller, the adaptive controller provided better disturbance rejection and set-point tracking and was able to control the superheating more efficiently, demanding less servomotor effort.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"22 1","pages":"424 - 434"},"PeriodicalIF":0.0,"publicationDate":"2014-01-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91216407","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}

{"title":"Comparison of performance characteristics of SCR and ECM controlled series fan powered terminal units","authors":"D. O’Neal, J. Edmondson, Peng Yin","doi":"10.1080/10789669.2013.850959","DOIUrl":"https://doi.org/10.1080/10789669.2013.850959","url":null,"abstract":"Airflow, efficiency, power, and power quality characteristics were evaluated for two variable air volume series fan powered terminal units. The power and power quality data included real power, power/airflow, apparent power, harmonic frequencies, and total harmonic distortion. Each unit had the same sized primary air inlet and were provided by the same manufacturer. One unit had a motor controlled by a silicon controlled rectifier and the other had an electronically commutated motor. Data were collected at a fixed downstream static pressure and a range of upstream static pressures, primary inlet damper positions, and input controller voltages. Both controllers maintained a nearly constant fan airflow as the primary air was varied. Fan/motor efficiencies were low (below 35%) and increased with fan static pressures. The electronically commutated motor unit had efficiencies as much as four times higher than the silicon controlled rectifier controlled unit which was reflected in much lower power draws. The electronically commuted fan/motor unit had the lowest apparent power at airflows below approximately 1000 ft3/min (0.47 m3/s). For both units, the total power harmonic distortion was less than 1%. The performance data indicated a major advantage of units with electronically commutated motors.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"17 2 1","pages":"194 - 202"},"PeriodicalIF":0.0,"publicationDate":"2014-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"90468090","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}

{"title":"Good design is only part of the story","authors":"M. Cook","doi":"10.1080/10789669.2014.870831","DOIUrl":"https://doi.org/10.1080/10789669.2014.870831","url":null,"abstract":"We spend a large proportion of our lives indoors and yet, many people do not realize the adverse effects that poor indoor air quality (IAQ) can have on our day-to-day well-being and productivity. W...","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"11 1","pages":"177 - 177"},"PeriodicalIF":0.0,"publicationDate":"2014-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76034049","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}

{"title":"Experimental investigation of aqueous LiBr solution absorber bundle with horizontal elliptical tubes","authors":"M. H. Abyaneh, M. Saidi, Cyrus Aghanajafi","doi":"10.1080/10789669.2013.868288","DOIUrl":"https://doi.org/10.1080/10789669.2013.868288","url":null,"abstract":"This article reports on the results of experimental studies on combined heat and mass transfer in the absorption of water vapor by aqueous LiBr solution under laminar falling film flow on the horizontal elliptical tube (HET) bundle. The performance of the absorber with HET has been calculated based on the measured parameters. The outputs are shown with respect to absorbent inlet mass concentration and Reynolds Number (Re), coolant inlet temperature and flow rate, and absorber vapor pressure. The results are compared with the published experimental results on absorber bundle with horizontal circular tubes (HCT). The results show that the heat and mass transfer coefficients enhanced on HET at aspect ratio (Ar ) > 1 with respect to HCT and improve with the increase of absorbent mass flow rate, absorber vapor pressure, coolant flow rate, and also with the decrease of absorbent concentration and coolant inlet temperature. Because of film thickness increasing and droplet flying off from the tube bundle, the maximum heat transfer coefficient is attained in an optimum absorbent mass flow rate around Re = 45. Finally, the empirical correlations for outside Sherwood number (Sh) and Nusselt number (Nu) are found to depend on the Re, Schmidt number (Sc), mass concentration and absorber vapor pressure.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"239 1","pages":"251 - 263"},"PeriodicalIF":0.0,"publicationDate":"2014-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76942122","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}

{"title":"The germicidal effects of microwave heating on microbes on evaporative humidifier elements","authors":"Yoonkyung Kang, S. Kato","doi":"10.1080/10789669.2013.862137","DOIUrl":"https://doi.org/10.1080/10789669.2013.862137","url":null,"abstract":"To identify the germicidal effects of microwave radiation for evaporative humidifiers, we measured the germicidal effects of fungal spores of Fusarium solani and vegetative cells and spores of the bacterium Bacillus subtilis using a mock-up system. The germicidal effect was compared to the output powers, irradiation times, and water contents of the element to establish effective disinfection conditions of humidifier element surfaces. The results demonstrated that the fungal and bacterial strains were inhibited at 1200 W for 20 min, except for the B. subtilis spores under the nonoperation condition involving water spray and the blower. In general, the germicidal effects appear to be stronger on the upper portion of the elements than on the lower portion. The germicidal effect was stronger at higher output power and longer exposure time under wet conditions. To achieve a uniform disinfection on the element faces, it is necessary to consider variations of these methods to produce a uniform heating pattern.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"8 1","pages":"230 - 237"},"PeriodicalIF":0.0,"publicationDate":"2014-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80168602","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}

{"title":"An optimal control strategy based on virtual flow measuring for variable flow primary pumping","authors":"Huojun Yang, Yifin Shi, Josephine Lau, Tian C. Zhang","doi":"10.1080/10789669.2013.874245","DOIUrl":"https://doi.org/10.1080/10789669.2013.874245","url":null,"abstract":"A virtual flow measuring is integrated with the best efficiency staging and the loop differential pressure (DP) reset method to unleash pump power saving potentials from a variable flow primary pump system. Based on the measured pump head, speed, and power, the virtual measuring determines the pump operation condition in an accurate and fast way. The pump operation parameters are then used to realize the best efficiency staging and the loop DP reset control, which calculate the optimal number of operating pumps and each pump's speed respectively. Simulation shows that this control strategy is most energy efficient, and it saves on pump energy consumption by 74.8% compared with a constant flow pumping system. The experiment from a retrofitted two-pump system also shows that the control strategy provided 64.5% pump energy saving over the original constant flow system. In addition, this control strategy requires a lower initial cost, simplifies the implementation process, makes system operation more reliable and stable, and reduces maintenance demands.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"23 1","pages":"411 - 423"},"PeriodicalIF":0.0,"publicationDate":"2014-01-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81952890","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}

{"title":"Stability and accuracy of variable air volume box control at low flows. Part 1: Laboratory test setup and variable air volume sensor test","authors":"Ran Liu, Jin Wen, Xiaohui Zhou, C. Klaassen","doi":"10.1080/10789669.2013.790736","DOIUrl":"https://doi.org/10.1080/10789669.2013.790736","url":null,"abstract":"Variable air volume systems with direct digital controllers have been widely adopted in the HVAC system of commercial, industrial, and large residential buildings because they provide better energy efficiency and occupant comfort. Normally, a variable air volume terminal unit defines a minimum airflow rate to satisfy the space ventilation requirement and/or the proper operation of a terminal heating coil, if so equipped. However, it has been found that variable air volume terminal units often fail to perform as expected at the minimum airflow range (below 500 fpm [2.5 m/s]). Under such a flow range, the embedded airflow sensor becomes inaccurate, and the designed minimum airflow rate is less than the minimum controllable airflow rate. This results in a series of problems, including lack of ventilation, uneven airflow control, reduced damper and operator life, and energy waste. Through designed laboratory and field tests, this study (ASRHAE Research Project RP-1353) aims to identify the major factors that cause inaccuracy and instability issues in variable air volume terminal units and the relationship between the major factors and performance of the airflow sensor, controller, and terminal unit system. Laboratory tests performed in this study included a variable air volume sensor test, controller test, and system test. Four variable air volume boxes from three manufacturers and four controllers from four manufacturers were tested systematically. Two identical test beds with high accuracy (±0.5%) reference airflow meters were designed and constructed in the test facility. The size of the reference airflow measuring stations was carefully selected to provide maximum airflow measuring accuracy and maximum available system pressure drop. This article describes the laboratory test setup and summarizes the variable air volume sensor test results. A companion article summarizes the controller test, system test, and field test results. From the variable air volume sensor test, three factors, namely, inlet conditions, low variable air volume damper positions, and low airflow rates, are identified as strongly impacting variable air volume terminal unit performance.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 1","pages":"18 - 3"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80229573","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}

{"title":"Stability and accuracy of variable air volume box control at low flows. Part 2: Controller test, system test, and field test","authors":"Ran Liu, Jin Wen, Xiaohui Zhou, C. Klaassen, Adam Regnier","doi":"10.1080/10789669.2013.794087","DOIUrl":"https://doi.org/10.1080/10789669.2013.794087","url":null,"abstract":"This article with its companion paper (Liu et al. 2013), summarizes the findings of ASHRAE Research Project 1353 (Stability and Accuracy of VAV Box Control at Low Flows). This project aims to identify the major factors that cause the airflow measurement in a variable air volume system to be inaccurate and unstable, especially at low airflow conditions. Both a laboratory test (including variable air volume sensor test, controller test, and system test) and field test were conducted; the companion work discussed the variable air volume sensor test. In this article, findings from the controller test, system test, and field test are summarized. The controller tests involved testing of four controllers from four different manufacturers. Testing was performed for accuracy, stability, resolution, and ambient temperature effect. For the system test, the variable air volume box and the controller were operated together and tested as terminal unit systems. Two terminal units were tested, and it was found that the performance of a variable air volume terminal unit is highly dependent upon on controller performance. Zeroing and balancing at a low airflow rate 560 fpm (2.84 m/s) or 200 cfm (0.09 m3/s) for an 8-in. (0.2-m) box were effective for achieving high system accuracy at low airflow ranges. For the field tests, five variable air volume terminal units were tested in real commercial buildings. It was found that system balancing was not always an effective way to reduce the variable air volume airflow sensor error in the field due to the uncertainty of reference airflow measurement methods commonly adopted in the field testing and balancing process.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"14 1","pages":"19 - 35"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72711184","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}

{"title":"Investigation on variable flow control in existing water-cooled chiller plant of high-rise commercial building in subtropical climate","authors":"K. F. Fong, C. K. Lee, T. Chow","doi":"10.1080/10789669.2013.822253","DOIUrl":"https://doi.org/10.1080/10789669.2013.822253","url":null,"abstract":"An all-variable-speed chiller plant has been advocated so that the chillers and their associated pumps can work at reduced speed during part-load conditions for energy saving purposes. In this new building project, the savings merit is certainly attractive. However, an existing chiller plant or retrofit project, which is constrained by the performance of installed equipment and the configuration of a hydronic circuit, may not benefit from the an ideal extent of savings. As such, an existing chiller plant serving a typical commercial building was used to evaluate this. Through year-round dynamic simulation, it is found that there were about 5%, 6%, and 8% energy savings of the whole chiller plant when applying variable flow control on secondary chilled water pumps only, both primary and secondary chilled water pumps, and all chilled and condenser water pumps, respectively. If constant-speed centrifugal chillers were substituted by the variable-speed ones, an additional 4% savings could be achieved, which was, however, less than that incurred from the associated pumps. The payback periods of different variable flow control strategies were well below 1 year, indicating the techno-economical feasibility for wider application in existing chiller plants in subtropical climates.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"44 1","pages":"51 - 60"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85591183","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}

{"title":"Removal characteristics of particulate matter with different return air system designs in a nonunidirectional cleanroom for integrated circuit (Ic) testing processes","authors":"Shih-cheng Hu, Y. Shiue, A. Shiue, Ming-Heng Tsai","doi":"10.1080/10789669.2013.840523","DOIUrl":"https://doi.org/10.1080/10789669.2013.840523","url":null,"abstract":"In a conventional arrangement of the airflow pathway in nonunidirectional airflow cleanrooms with wall return schemes, the supply air is introduced from ceiling air grills and the return air, close and vertical to the floor, is extracted from the wall air grills. However, such a wall return ventilation system is theoretically not an optimal design for removing heat and particles released from processing machinery. The conventional wall return system currently used in cleanrooms aims to create an environment with diluted particle concentration in which downward cold supply air from ceiling filters encounters upward air currents generated by drifted particles from processing machinery. To solve the problem, we introduced a new design called fan dry coil units (FDCUs). In this article, we compare the performances of both innovative and traditional ventilation systems in a full-scale cleanroom. For each return air ventilation system, we investigated the effects of air change rates on the removal of 0.1∼5 μm particles. Based on the results, it is noted that the FDCU-return system eliminates about 60% more particles from the cleanrooms, compared with conventional wall-return system.","PeriodicalId":13238,"journal":{"name":"HVAC&R Research","volume":"1 4","pages":"162 - 166"},"PeriodicalIF":0.0,"publicationDate":"2014-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72600294","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}