• 제목/요약/키워드: frosting

검색결과 82건 처리시간 0.023초

착상을 수반한 핀-관 열교환기의 성능평가계수에 관한 연구 (The Study of Performance Evaluation Coefficient of Fin-and-Tube Heat Exchangers with Frosting)

  • 최봉준;황준현;신종민
    • 설비공학논문집
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    • 제15권2호
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    • pp.132-136
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    • 2003
  • For the study of performance evaluation on different shape heat exchangers that have the same energy consumption in a refrigerator, we make performance evaluation coefficient (PEC) which can distinguish performance of different shape heat exchangers. The results were reported in order to compare with for the dry frosting and wet frosting test as various definition of PECs. Results showed that PEC of dry frosting test is higher than that of wet frosting test because attached water droplet increases pressure drop of air-side then this decreases performance of heat exchanger.

냉각면 평판에서 착상 지연을 위한 임계공기온도 상관식 (Correlation of Critical Air Temperature for Frost Delay on a Cold Plate)

  • 김정수;김유일;김욱중;이관수
    • 대한기계학회논문집B
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    • 제30권12호
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    • pp.1188-1195
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    • 2006
  • This paper examines the critical air temperature at which frost formation does not occur on a cold plate in order to improve the efficiency of a heat pump. The critical air temperature on test points is obtained from numerical analysis and a correlation of the critical air temperature is derived as a function of frosting factors (air absolute humidity, air velocity, and cold plate temperature) by least square method. Experiments are carried out to verify the correlation proposed in this study, and the prediction obtained with the correlation agrees well with the experimental data. Based on the correlation, we propose the non-frosting regions according to frosting factors.

쇼케이스의 적상 및 제상 특성 (Frosting and defrosting characteristics of a showcase system)

  • 노현일;박윤철;김용찬
    • 대한기계학회:학술대회논문집
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    • 대한기계학회 2000년도 추계학술대회논문집B
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    • pp.309-313
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    • 2000
  • An experimental study was conducted to analyze the characteristics of the showcase refrigeration system during frosting and defrosting process. Test showcase was constructed with a cooling capacity of 3RT including 3 evaporators. The dynamic characteristics of the system under frosting and defrosting conditions were investigated. Refrigerant temperature and pressure of the system, dry bulb and wet bulb temperature of air passing through the evaporator, air flow rate and compressor power were measured.

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휜-관 열교환기의 착상 성능 해석 (Analysis of Frosting Performance of a Fin-Tube Heat Exchanger)

  • 양동근;이관수
    • 설비공학논문집
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    • 제17권11호
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    • pp.965-973
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    • 2005
  • This paper proposes a mathematical model for predicting the frosting performance on a fin-tube heat exchanger. The model consists of empirical correlations of average heat transfer coefficients for the plate and tube surfaces and a diffusion equation inside the frost layer. The numerical results are compared with experimental data for the frost thickness, the frosting rate and the heat transfer rate to validate the proposed model. The results are in good agreement with the experimental data, and show that this model can be applied to predict frosting performance of common fin-tube heat exchanger.

휜-관 열교환기의 착.제상 거동에 대한 표면처리의 영향에 관한 실험적 연구 (An Experimental Study of the Surface Treatment Effect on the Frosting/Defrosting Behavior of a Fin-Tube Heat Exchanger)

  • 지성;이관수
    • 대한기계학회논문집B
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    • 제24권8호
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    • pp.1062-1068
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    • 2000
  • The effect of heat exchanger surface treatment on the frosting/defrosting behavior in a fin-tube heat exchanger is investigated experimentally. It is found that the hydrophilic surface mainly influences on the frosting behavior, however, the hydrophobic surface gives some influence on the defrosting behavior. In view of frosting performance, surface-treated heat exchanger with either hydrophilic or hydrophobic characteristic shows a little improvement in the thermal performance than the aluminium heat exchanger with no surface treatment. The result reveals that the heat exchanger with hydrophobic surface treatment is more effective in view of the defrosting efficiency and time. The amounts of residual water on the surface-treated heat exchangers are shown to be smaller than those of the bare heat exchanger, therefore further improvements on the performance of re-operations are expected.

착상을 수반한 멀티 가변속 열펌프의 동특성 (A Dynamic Characteristic of the Multi-Inverter Heat Pump with Frosting)

  • 박병덕;이주동;;황일남;장세동;황정하
    • 설비공학논문집
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    • 제15권5호
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    • pp.337-345
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    • 2003
  • In the case of heat exchangers operating under frosting condition, the growth of frost layer causes the heat exchanger to increase the thermal resistance and pressure loss of the air flow. In this paper, a transient characteristic prediction model of the heat transfer for multi inverter heat pump with frosting on its surface was presented taking into account the change of the fin efficiency due to the growth of the frost layer. In this dynamic simulation program, which was peformed for a basic air conditioning system model, such as evaporator, condenser, compressor, linear electronic expansion valve (LEV) and bypass circuit. The theoretical model was driven from the obtained heat transfer coefficient and mass transfer coefficient, independently. And we consider heat transfer performance was only affected by a decrease of the wind flow area. The calculated results were compared with some cases of experiments for frosting conditions.

Development of the Dynamic Simulation Program of a Multi-Inverter Heat Pump under Frosting Conditions

  • Park Byung-Duck;Lee Joo-Dong;Chung Baik-Young
    • International Journal of Air-Conditioning and Refrigeration
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    • 제12권3호
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    • pp.113-122
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    • 2004
  • In case of heat exchangers operating under frosting condition, the thermal resistance and the air-side pressure loss increase with a growth of frost layer. In this paper, a transient characteristic prediction model of the heat transfer for a multi-inverter heat pump with frosting on its surface was presented by taking into account the change of the fin efficiency due to the growth of the frost layer. This dynamic simulation program was developed for a basic air conditioning system composed of an evaporator, a condenser, a compressor, a linear electronic expansion valve, and a bypass circuit. The theoretical model was derived from measured heat transfer and mass transfer coefficients. We also considered that the heat transfer performance was only affected by the decrease of wind flow area. The calculated results were compared with the experimental results for frosting conditions.

핀-관 열교환기에 대한 제상 거동에 관한 실험적 연구 (An experimental study of behavior of defrosting on the fin-tube heat exchanger)

  • 이관수;김규우;지성
    • 설비공학논문집
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    • 제10권6호
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    • pp.649-657
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    • 1998
  • In this study, the effects of the various conditions of frosting and defrosting on the behavior of defrosting in a fin-tube heat exchanger have been examined experimentally. The electric heater is used for defrosting in a fin-tube heat exchanger It is shown that there are several local maxima in the water draining rate. The amount of residual water on the heat exchanger after the completion of defrosting is kept constant due to surface tension on the heat exchanger. Without considering the degradation of the thermal performance due to the frosting, the defrosting efficiency is improved with increasing amount of the frost irrespective of the frosting condition. The defrosting behavior is affected by the frosting density as well as the frost accumulation, which vary with the experimental operating conditions during the frosting period. The heat loss to the surrounding air decreases, and the melting and defrosting efficiencies show high values with decreasing heat input.

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착상시 설계인자에 따른 핀-관 열교환기의 성능변화에 관한 실험적 연구 (An Experimental Study on the Effects of Design Factors for the Performance of Fin-Tube Heat Exchanger Under Frosting Conditions)

  • 이관수
    • 대한기계학회논문집
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    • 제19권10호
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    • pp.2657-2666
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    • 1995
  • In this study, the effects of design factors of finned-tube heat exchanger, such as fin spacing and fin array on the frost growth and heat exchanger performance are investigated under a frosting condition. The results show that the amount of frost, frost density and blockage ratio of air flow passage increase with decreasing fin spacing. Heat transfer rate increases momentarily at the initial stage of frosting and then decreases. After that heat transfer rate continues to increase again to reach a maximum value and then decreases dramatically. It is shown that the time required for heat transfer rate to reach a maximum value becomes shorter with decreasing fin spacing, and after a maximum value, heat transfer rate decreases very fast. The maximum allowable blockage ratio is introduced to determine the operation limit of a finned-tube heat exchanger operating under frosting condition and is obtained as a function of fin spacing. It is also shown that heat transfer rate of heat exchanger with staggered fin array increases about 17% and the amount of pressure drop of air increases about 1~2 mmH$_{2}$O, compared with those of in-line type heat exchanger under frosting condition.

A Review on the Performance of Fin-and-Tube Heat Exchangers Under Frosting and Defrosting Conditions

  • Kim, Yong-Chan;Lee, Ho-Seong
    • International Journal of Air-Conditioning and Refrigeration
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    • 제13권3호
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    • pp.152-157
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    • 2005
  • This paper reviews the literature on the performance of fin-and-tube heat exchangers under frosting and defrosting conditions. The effects of frosting and defrosting on the following parameters were discussed: frost growth, overall heat transfer coefficient, surface roughness, and surface characteristics on the heat exchanger. Comparisons of the experimental results and empirical correlations that were obtained from open literature were presented. In addition, a review of the defrosting methods was conducted.