相变蓄热在热泵空调系统中的应用研究

发布时间：2018-04-10 17:49

本文选题：相变蓄热 + 冷凝热回收　；参考：《天津商业大学》2014年硕士论文

【摘要】：能源与环境问题随着经济的迅速发展和社会的进步日益突出，因此利用新的节能技术来提高能源利用率，降低常规能源消耗是能源实现可持续发展的重要措施。由于相变蓄热材料储能密度高、安全、经济且性能稳定，可以解决能源供应在时间与空间上不匹配的问题，对提高能源利用率有很高的研究意义和广阔的应用前景。热泵技术的节能和环保特点在诸多领域得到广泛应用，在制取生活热水方面的应用也在逐渐收到重视。而当下的热泵热水器存在水箱占用建筑空间大，系统运行不平稳等缺点，为了改善这些缺点本文将相变蓄热技术与热泵技术相结合，研究相变蓄热式空气源热泵冷凝热回收，优化系统运行性能并提高冷凝废热利用率。本文所做的研究工作是以相变蓄热式热泵空调冷凝热回收系统为对象，结合相变蓄热技术对常规空气源热泵空调系统进行性能实验和模拟研究。文中冷凝热回收系统性能研究均是针对部分冷凝热回收模式展开的，通过实验测试与数值计算的研究方法来对该冷凝热回收系统的换热特性进行深入研究，主要研究工作如下： 1、对相变传热过程进行热工特性分析，得出相变蓄热技术的特点，以及相变蓄热箱的传热系数计算式。采用差示扫描量热法（DSC）对相变材料热物性参数进行测定，实验结果显示材料熔点为59℃，凝固点为54.3℃，相变潜热值为187kJ/kg，从而为后期系统性能的计算提供了理论依据。 2、对相变蓄热热泵空调系统开展蓄热特性实验研究。实验采用模拟室内外环境工况的方法，对系统进行冷凝热回收实验。结果表明系统平均综合能效系数COPt为3.35，平均冷凝热回收率为20%。同无冷凝热回收热泵空调系统制冷模式下的实验结果相比，系统平均综合能效系数由原来的2.4提高了约39.6%。从系统性能角度来看，将相变蓄热技术与传统热泵空调系统结合可以提高空调系统的综合性能。另外，相变材料在蓄热箱内的熔化情况表明，系统运行至10h，蓄热箱内的石蜡仍存在部分固态未融化。 3、对相变蓄热箱内石蜡的放热特性开展实验研究，通过改变蓄热箱冷水进口水温和水流量来对箱内石蜡的放热过程进行了实验测试。结果表明，增加水流量或者提高冷水进口水温可以缩短热水加热时间，增大水流量不改变冷水进水温度，热水出水时间可以缩短约1.6h；提高冷水进口水温水不改变水流量，获取热水时间缩短约3.3h。同时研究结果表明，在1h之内热水温升不大，约为2~3℃，可见换热效率很低。 4、对相变蓄热箱内换热过程建立了物理和数学模型，模拟计算有无自然对流现象的石蜡温度变化，并将考虑自然对流的计算结果与实验进行了比较。结果表明，模拟计算与实验结果近似相同，，误差在0.3%～7%之内，模拟计算有效。在石蜡蓄热过程中，箱内石蜡温度分层现象较重，最大温差达到32℃，可见蓄热箱换热效果并不理想，系统性能仍需进一步提高。
[Abstract]:Energy and environmental problems with the rapid development of economy and social progress have become increasingly prominent, therefore the use of new technologies to improve energy efficiency, reduce the consumption of conventional energy sources is an important measure to realize the sustainable development of energy. As the phase change material of high energy storage density, safety, economy and stable performance, can solve the energy supply does not match in time and space of the problem, the significance of the research is to improve the energy utilization rate is high and wide application prospect. The characteristics of energy saving and environmental protection heat pump technology has been widely used in many fields, the application in preparation of hot water has also gradually received attention. While the heat pump water heater of the present building space occupied by water tank large system, unstable operation and other shortcomings, in order to improve the shortcomings of the phase-change heat storage technology and heat pump technology combined with the research of phase change thermal storage type air source heat pump cold The condensing heat recovery is used to optimize the operating performance of the system and improve the utilization rate of condensing waste heat.
The work of this paper is to phase change condensing heat recovery heat pump air conditioning system as the object, combined with the phase change technology and simulation experiments of the conventional air source heat pump air conditioning system. In this paper, the performance of the system is on a part of the condensing heat recovery of condensing heat recovery mode, by using the method of test and numerical experiments the calculation of the heat transfer characteristics of the condensing heat recovery system of in-depth study, the main research work is as follows:
1, thermodynamic analysis on the characteristics of phase change heat transfer process, the characteristics of phase change thermal storage technology, and the calculation of phase change thermal storage box. The heat transfer coefficient by differential scanning calorimetry (DSC) of the phase change material thermophysical parameters were measured, experimental results show that the melting point of 59 DEG C, the freezing point is 54.3 DEG C, phase transition the latent heat value is 187kJ/kg, which provides a theoretical basis for the calculation of the late performance of the system.
2, the phase change heat pump air conditioning system to carry out experimental research on the characteristics of the regenerative method. Experiments using simulated indoor environment condition, for condensing heat recovery experiments on the system. The results show that the system average comprehensive energy efficiency coefficient of COPt was 3.35, compared to the average condensation heat recovery rate of 20%. with non condensing heat recovery heat pump air conditioning system under the mode of experiment the average comprehensive energy efficiency coefficient increased from 2.4 about 39.6%. from the performance point of view, the phase change heat storage technology with the traditional combination of heat pump air conditioning system can improve the comprehensive performance of air conditioning system. In addition, shows that the melting of phase change material in the heat storage tank and system operation to 10h, the heat storage tank is still a part of solid paraffin not melt.
3, to carry out the experimental study on heat transfer characteristics of phase change heat storage tank of paraffin, by changing the heat storage tank water inlet water temperature and flow of box paraffin exothermic process was tested. The results showed that the water flow rate increase or improve the cold water inlet water temperature hot water can shorten the heating time, increase the flow of water without changing the inlet temperature of cold water, hot water the time can be shortened about 1.6h; improve the cold water inlet water temperature does not change the water flow, reduce about 3.3h. the results also show that the access time within 1h hot water, hot water temperature is about 2~3 degrees, can see the heat transfer efficiency is very low.
4, the phase change heat transfer process inside a physical and mathematical model, the temperature change has no paraffin simulation of natural convection, and will consider the results of natural convection are compared with experiments. The results show that the simulation and experimental results are approximately the same, the error in the range from 0.3% to 7%, effective simulation in the process of paraffin storage box, paraffin temperature stratification is heavy, the maximum temperature reached 32 degrees, the visible heat storage tank heat transfer effect is not ideal, still need to further improve the system performance.

【学位授予单位】：天津商业大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TU831

【参考文献】