Improving reverse cycle defrosting performance of air source heat pumps using thermal storage-based refrigerant sub-cooling energy
Improving reverse cycle defrosting performance of air source heat pumps using thermal storage-based refrigerant sub-cooling energy
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DOI：
10.1177/0143624411406016
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发表时间：
2012-05
影响因子：
1.7
通讯作者：
Dong Jiankai;J. Yiqiang;D. Shiming;Yao Yang;Qu Minglu
中科院分区：
文献类型：
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作者：
Dong Jiankai;J. Yiqiang;D. Shiming;Yao Yang;Qu Minglu
空气源热泵机组在冬季环境温度较低的情况下用于采暖时，室外盘管表面可能会结霜。随着时间的推移，盘管表面上的霜积聚可能足以限制空气通过盘管，并增加环境空气与盘管表面之间的传热阻力，导致室外盘管的性能下降，甚至导致空气源热泵机组停机。因此，定期检查是必要的。目前，用于ASHP单元的最广泛使用的标准除湿方法是逆循环除湿。在标准的逆循环热泵（SRCD）运行期间，ASHP单元中的室内盘管实际上充当蒸发器。由于在制冷期间室内风扇通常被关闭，因此来自室内盘管的能量的量微不足道，从而导致许多相关的操作问题，例如制冷持续时间较长以及在制冷期间加热空间内的空气温度较低的风险等。为了解决制冷期间可用热量不足的基本问题，同时确保系统高效和安全地操作，已经开发了一种新的逆循环制冷（NRCD）方法，该方法是基于热能存储的，其使用用于ASHP的制冷剂的过冷能量。使用SRCD方法和NRCD方法的比较实验进行了一个实验ASHP单位与标称2.5千瓦的供热能力。实验结果清楚地表明，当使用NRCD方法时，排出和吸入压力分别增加了0.56和0.12 MPa。与采用SRCD方法相比，该方法的间歇运行时间和恢复运行时间分别缩短了30.8%和25.0%，间歇运行能耗降低了13.9%。实际应用：ASHP因其显著的节能潜力而在世界范围内得到广泛应用。然而，当空气源热泵机组用于空间加热时，在室外盘管表面上可能形成霜。盘管表面积霜会降低盘管效率，甚至造成机组停机。逆循环法是应用最广泛的标准循环法。介绍了一种在供热运行时作为过冷器、在回热运行时作为热源的PCM-HE型空气源热泵机组的逆循环回热性能，为保证机组的安全运行和提高回热效率提供了依据。
When an air source heat pump (ASHP) unit is used for space heating at a low ambient temperature in winter, frost may be formed on its outdoor coil surface. Over time, frost accumulation on coil surface may become sufficient to restrict air passage through the coil and increase the heat transfer resistance between ambient air and coil surface, leading to performance degradation for the outdoor coil, or even the shutdown of the ASHP unit. Therefore, periodic defrosting is necessary. Currently, the most widely used standard defrosting method for an ASHP unit is reverse cycle defrosting. During a standard reverse cycle defrosting (SRCD) operation, the indoor coil in an ASHP unit actually acts as an evaporator. Because the indoor fan is usually turned off during defrosting, there is an insignificant amount of energy from indoor coil, leading to a number of associated operational problems such as a longer defrosting duration and the risk of having a lower air temperature inside a heated space during defrosting, etc. To solve the fundamental problem of insufficient heat available during defrosting while ensuring the efficient and safe system operation, a novel reverse cycle defrosting (NRCD) method which is thermal energy storage-based using sub-cooling energy of refrigerant for ASHPs has been developed. Comparative experiments using both the SRCD method and the NRCD method were carried out on an experimental ASHP unit with a nominal 2.5 kW heating capacity. Experimental results clearly suggested that when using the NRCD method, the discharge and suction pressures were increased by 0.56 and 0.12 MPa, respectively. Furthermore, the defrosting duration and heating-resumption duration were shortened by 30.8% and 25.0%, respectively, and the defrosting energy consumption was reduced by 13.9%, compared to those when using the SRCD method. Practical application: ASHPs have been widely used worldwide due to their significant energy-saving potentials. However, frost can be formed on the outdoor coil surface when an ASHP unit operates for space heating. Frost accumulation on coil surface reduces the coil’s efficiency, or causes even the shutdown of the ASHP unit. Reverse cycle defrosting is the most widely used standard defrosting method. This paper presents the reverse cycle defrosting performance for an ASHP unit with a PCM-HE acting as both a sub-cooler during heating operation and a heat source during defrosting operation, which could help to ensure the safe operation and achieve a higher defrosting efficiency of the ASHP unit.