The Experts below are selected from a list of 45 Experts worldwide ranked by ideXlab platform

Chen Zhen-kai - One of the best experts on this subject based on the ideXlab platform.

  • Effect of air temperature and humidity on system defrosting characteristics of a PCM based air source heat pump
    Journal of the Harbin Institute of Technology, 2020
    Co-Authors: Chen Zhen-kai
    Abstract:

    The experiments were carried out to test the effect of air temperature and humidity on a novel PCM based Reversed-Cycle defrosting for air source heat pump(ASHP),and the results showed that PCM based Reversed-Cycle defrosting method could keep the suction pressure of compressor higher than 0.35 MPa,which was father higher than the system's low suction protection pressure.The system's defrosting time and energy consumption increased with the relative humidity when air temperature was kept constant.Furthermore,the system's defrosting time and energy consumption increased first and then decreased with the decrease of air temperature,and the most defrosting time and energy were consumed when the outdoor air temperature was-3 ℃.It could be concluded that the air temperature and humidity affected the defrosting process greatly and the system's reliability was improved greatly because shutting down of ASHP unit due to low suction pressure protection during defrosting could be effectively avoided by the PCM based heat exchanger,and-3 ℃ working condition could be selected as the most adverse design condition for the PCM based heat exchanger when the relative humidity was constant because the most defrosting time and energy were needed.

Sun Cheng - One of the best experts on this subject based on the ideXlab platform.

  • Study on Thermal Energy Storage Modes and Defrosting Dynamic Characteristics of a PCM Based Air Source Heat Pump
    Building Science, 2020
    Co-Authors: Sun Cheng
    Abstract:

    In this paper,a novel phase change material(PCM) based Reversed-Cycle defrosting method for air source heat pump(ASHP) was introduced and its PCM based heat exchanger(PCMHE) was designed.Three thermal energy storage modes were presented and experiments were carried out to test the efficiencies of thermal energy storage and defrosting respectively.By analyzing the experiment results,it was concluded that energy could be quickly stored in PCMHE with series thermal energy storage mode.Nevertheless,with sole and parallel modes,discharge and suction temperatures of the compressor were unusually high,while discharge and suction pressures and input power were relatively lower,also the thermal energy storage speed was very small,which meant that the ASHP could not work effectively.Furthermore,by comparing the PCM based Reversed-Cycle defrosting method with the traditional one,it was indicated that the former could decrease the defrosting time by 4 minutes at least,also shutting down of the ASHP unit due to low suction pressure protection could be avoided effectively by increasing the compressor's suction pressure of 0.3 MPa.Besides,when the system returned to the heating supply mode from the defrosting mode,with the PCM based defrosting method,the air temperature out of the indoor coil increased faster and was higher than the traditional method,which would benefit the indoor thermal comfort greatly.

Chang-duk Jeon - One of the best experts on this subject based on the ideXlab platform.

  • AN EXPERIMENTAL STUDY ON PERFORMANCE IMPROVEMENT FOR AN AIR SOURCE HEAT PUMP BY ALTERNATE DEFROSTING OF OUTDOOR HEAT EXCHANGER
    International Journal of Air-conditioning and Refrigeration, 2014
    Co-Authors: Hoon Jung, Jungho Hwang, Chang-duk Jeon
    Abstract:

    For a space heating air source heat pump (ASHP) in the condition of low temperature and high humidity, frost on the surface of heat exchanger becomes the major cause decreasing heating surface area and thus the performance of heat pump. In this study, we showed a method of delaying the implantation of frost using alternate defrost control. First, we acquired the performance data for conventional periodic Reversed-Cycle defrosting with a 5RT heat pump. After the experiment, the heat pump was modified to verify the effects of newly introduced alternate defrosting and compared with the conventional periodic reverse Cycled method. It was found that heating coefficient of performance (COP) of heat pump using newly proposed alternate defrost method was about 17% higher than conventional heat pump using periodic reverse Cycled defrosting.

Hoon Jung - One of the best experts on this subject based on the ideXlab platform.

  • AN EXPERIMENTAL STUDY ON PERFORMANCE IMPROVEMENT FOR AN AIR SOURCE HEAT PUMP BY ALTERNATE DEFROSTING OF OUTDOOR HEAT EXCHANGER
    International Journal of Air-conditioning and Refrigeration, 2014
    Co-Authors: Hoon Jung, Jungho Hwang, Chang-duk Jeon
    Abstract:

    For a space heating air source heat pump (ASHP) in the condition of low temperature and high humidity, frost on the surface of heat exchanger becomes the major cause decreasing heating surface area and thus the performance of heat pump. In this study, we showed a method of delaying the implantation of frost using alternate defrost control. First, we acquired the performance data for conventional periodic Reversed-Cycle defrosting with a 5RT heat pump. After the experiment, the heat pump was modified to verify the effects of newly introduced alternate defrosting and compared with the conventional periodic reverse Cycled method. It was found that heating coefficient of performance (COP) of heat pump using newly proposed alternate defrost method was about 17% higher than conventional heat pump using periodic reverse Cycled defrosting.

Jiang Yan Li - One of the best experts on this subject based on the ideXlab platform.

  • The Iterative Method for Reliability Estimation of Fatigue Life
    Applied Mechanics and Materials, 2012
    Co-Authors: Peng Xu, Jiang Yan Li
    Abstract:

    The expression of reliability estimation method for fatigue life of machine parts was derived, and two kinds of stress Cycles (Reversed Cycle and un-symmetric Reversed Cycle) were considered. An iteration method is presented and the corresponding computer program named STRENGTH-2 is developed for estimating reliable life of machine parts. The engineering application results show that the calculated results are close to experimental results. The proposed method can be convenient to carry out the fatigue reliability design for machine parts under the action of uni-axial and multi-axial loadings, and promote the popularization and application of existing anti-fatigue design method. It has the high value of engineering application.