Defrosting method adopting dual hot gas bypass for an air-to-air heat pump

Choi, Hwan-Jong; Kim, Byung-Soon; Kang, Dong-Joo; Kim, Kyung Chun

doi:10.1016/j.apenergy.2011.05.039

Cited by 93 publications

(14 citation statements)

References 12 publications

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“…T f and T df correspond to the frosting and defrosting time in one operation cycle, respectively. Assuming that whether in frosting or defrosting process, the electricity consumption of compressor and the heat release of the condenser are stable in a certain time (ΔT f and ΔT df ), and the whole process is regarded as an approximate steady state process, and the systems EER f , EER df , and EER of the different processes are expressed as (6), (7), and (8), respectively.…”

Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

“…Therefore, the identification of the most suitable and effective defrosting method is of widespread concern. The defrosting methods mainly include hot water spray defrosting, electric heater defrosting, compressor shutdown, hot gas bypass and reverse‐cycle defrosting . A number of studies have experimentally investigated the defrosting methods and their effects .…”

Section: Introductionmentioning

confidence: 99%

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Experimental study on the performance of air source heat pump system with multiple parallel outdoor units

Niu

2020

Int J Energy Res

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Summary This paper presents a novel air source heat pump for heating of buildings named air source heat pump with multiple parallel outdoor units (ASHPMO). Multiple outdoor units were connected in parallel with the aim of realising alternate defrosting and uninterrupted heating simultaneously. An experimental apparatus of the ASHPMO system was developed. The defrosting performance was experimentally investigated under different outdoor air temperatures, outdoor air relative humidity, and condensation temperatures, among other factors. The test results showed that the novel ASHPMO system could provide continuous heating when defrosting even under an outdoor air temperature of −10°C. Variations in compressor vapour suction and discharge pressure and temperature were observed. The minimum heating capacity could still reach 60% of that without defrosting. Under the defrosting condition with outdoor air temperature −10°C, both the heating coefficient of performance (heating COP) and total energy efficiency ratio (EER) of the system can reach to 2.0 and 2.32, respectively.

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Section: Experimental Apparatus and Proceduresmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Experimental study on the performance of air source heat pump system with multiple parallel outdoor units

Niu

2020

Int J Energy Res

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“…Then a defrosting cycle combined dual hot gas bypass defrosting (DHBD) and the accumulator heating method was developed . Compared with HGBD method, DHBD method reduced the defrosting time by 36% …”

Section: Introductionmentioning

confidence: 99%

“…24 Compared with HGBD method, DHBD method reduced the defrosting time by 36%. 25 Phase change energy storage defrosting has also been widely studied. In recent years, performance improvement and energy demand reduction in refrigeration systems using phase change material (PCM) has attracted more attention.…”

Section: Introductionmentioning

confidence: 99%

Experimental analysis of defrosting and heating performance of a solar‐assisted heat pump integrated phase change energy storage

Chen

Zhang

et al. 2019

Int J Energy Res

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Summary This thesis investigates a novel solar‐assisted heat pump integrated phase change energy storage system. The defrosting performance of this system was studied experimentally and the results were compared with two traditionally used methods: reverse cycle defrosting (RCD) method and hot gas bypass defrosting (HGBD) method. The results show that the phase change energy storage system has superior performance compared with traditional defrosting methods. The indoor temperature drop recorded was relatively small and the defrosting time was 75% of the RCD system and 53% of HGBD system. The phase change energy storage system increased the condensation temperature which consequently increased the temperature difference of heat transfer resulting in higher conductivity in the defrosting progress. Compared with the method of RCD and the method of HGBD, the recovery time of the system was shortened by 90 and 160 seconds, respectively. The system works with low‐temperature heat source and circulating water, which considerably reduces energy consumption, thereby improving the performance of the defrosting system. A further experimental study was also conducted on the heating performance and the results also indicated that the value of COP can reach up to 3.6 in daytime, and the indoor temperature can be stably maintained above 18°C throughout the day. Novelty Statement A new defrosting method for energy storage defrosting is proposed, and the defrosting performance is compared with two common defrosting methods. In addition, the performances of the heating system over the day were experimentally investigated. The experimental results show the system meets the heating needs of the building. Finally, the influence of the outdoor temperature on the exergy efficiency of the system was discussed. It shows that this system can improve the operational stability, the system economy and energy saving.

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“…In the refrigerating engineering field, Ma & Wang (2011) developed bypass check valve to enhance the overall system performance; Choi, B. Kim, Kang, & K. Kim (2011), and J. Kim, Choi, & K. Kim (2015) applied the bypass for defrosting in the heat pump; Tuo & Hrnjak (2012) showed that flash gas bypass method could improve refrigerant distribution and reduce pressure drop on refrigerant side in the mobile air conditioning system; Byun, Lee, & Jeon (2008) discovered that the hot gas bypass method was useful for retarding the formation and growth of frost at the outdoor coil and for improving the performance of the air source heat pump; Tso, Wong, Jolly, & Ng (2001) conducted simulation studies using a mathematical model to compare the performance of the hot-gas by-pass control and the suction modulation control in refrigerated shipping containers, their results showed that the suction modulation control strategy was the more energy efficient of the two; Elbel & Hrnjak (2004) found that the performance of transcritical R744 systems with direct expansion could be significantly improved by implementing a flash gas bypass; it was demonstrated by Wang, Han, Shi, & Li (2012) that suction gas bypass was an effective regulating method of scroll compressor, and it could reduce the inner compression loss under over compression conditions and largely decrease the heating/cooling capacity of the refrigeration system; used flash gas bypass for vapor-liquid separation in vapor compression systems; Huang, Li, & Yuan (2009) suggested that the hot-gas bypass defrosting could overcome the main disadvantages of the reverse-cycle defrosting method; Ding, Zhang, & Lu (2004) proved bypass two-circuit cycle freezers with one compressor were more efficient than two-evaporator in series cycle freezers in reducing the greenhouse gas emissions.…”

Section: Introductionmentioning

confidence: 99%

Adding a Bypass to Ensure the Chemical Plant Production

Wang¹,

Peng²,

Wang³

2016

IJC

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The chilling output of the chiller fluctuated according to the chilling load. When it dropped down below a certain value, the temperature of the supply chilled water flowing out of the chiller would drop down too much. And this would result the chiller being shut down abnormally, because of its low temperature protection. Any this shutdown of the chiller endangered the production continuity and security, and caused a certain economic losses. A bypass, which was from the outlet of the chiller's condenser to the chilled water filter inlet, was added to the chilling system. Through this bypass, some cooling water was introduced from the cooling water circulation into the chilled water circulation. Then the temperature of the supply chilled water flowing out of the chiller was promoted. With experiments, and by the aid of thermodynamics analysis, the amount of introduced cooling water, which could be introduced to promote the supply chilled water temperature for maintaining the chiller running normally, was researched. Ultimately, a certain amount of introduced cooling water, at which the chiller would no longer stop abnormally at any chilling load, was determined. And the energy lose caused by the introduced cooling water was less than 5 percent the rated output of the chiller. Compared with the chiller rated output, this energy lose was so small that it could be neglected.

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Defrosting method adopting dual hot gas bypass for an air-to-air heat pump

Cited by 93 publications

References 12 publications

Experimental study on the performance of air source heat pump system with multiple parallel outdoor units

Experimental study on the performance of air source heat pump system with multiple parallel outdoor units

Experimental analysis of defrosting and heating performance of a solar‐assisted heat pump integrated phase change energy storage

Adding a Bypass to Ensure the Chemical Plant Production

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