| This paper presents a self-coupling phase change heat storage heat pump system for intermittent heating buildings(schools,office buildings,etc.)with peak-valley electricity price.The system can switch freely between the operation modes of air source heat pump and water source heat pump by using phase change heat accumulator.In this paper,after a detailed introduction of the system operation principle,starting from the selection of refrigerant and phase change materials,the influence of water supply temperature,phase change temperature and day-night temperature difference on the system performance of conventional ultra-low temperature air source heat pump system and the self-coupling phase change heat storage heat pump system under the outdoor temperature of-25℃～10℃ is compared and investigated.Then select two typical city of Xi ’an and Lanzhou certain office building as the research object,through the De ST software modeling calculation of two typical city in the heating season after the hourly dynamic heat load,dynamic comparative analysis of the system in different city COP and peak valley price difference influence on economy,finally further exploration phase change heat storage device costs increase and water temperature variation on the system the influence law of investment recovery period.The following conclusions:(1)In terms of steady-state operation efficiency,compared with the conventional cryogenic air source heat pump system,this article system in-25℃ under the extreme outdoor environment of preparing 55℃ high temperature hot water COP is 1.74,higher than that of conventional air source heat pump system is above 0.7,performance is good,the higher the water temperature,in this paper,the performance of heat pump system increases,the greater the The influence of water supply temperature on COP of the system is higher than that of phase transition temperature.The COP value of the self-coupling phase change heat storage heat pump system is higher with the lower phase change temperature at-25℃～-10℃,and the COP value is higher with the higher phase change temperature at-10℃～10℃.Phase transition temperature has little effect on diurnal temperature difference.The smaller the temperature difference between day and night,the higher the water supply temperature,the better the performance of the new system;(2)In terms of steady-state economy,the effect of phase transition temperature on COP is relatively small under the same diurnal temperature difference;The temperature difference between day and night decreases,and the higher the water supply temperature,the better the performance of the new system.The smaller the fluctuation of temperature difference between day and night,the wider the range of the unit heating cost of the new system is lower than the outdoor temperature of the conventional system.The lower the outdoor temperature is,the higher the water supply temperature is.compared with the conventional ultra-low temperature air source heat pump system,the larger the reduction range of unit heating cost of the new system is,the more the operation cost is saved.Phase change temperature changes will have little impact on the new system unit quantity of heating costs,increased by 18℃to 23℃,the change of no more than 3%;(3)In dynamic research,under the water temperature of 55℃,the system in Xi ’an and Lanzhou area average COP value above2.0,and winter outdoor temperature is lower,the system COP difference difference,the more obvious;After adopting peak-valley electricity price policy,compared with conventional ultra-low temperature air source heat pump system,the total operating cost in heating season is reduced by more than 30%.In addition,the peak-valley electricity price difference in Lanzhou is greater than that in Xi ’an,and the peak-valley electricity price difference has a greater impact on the economy of the system.The economic benefit of the heat pump system in this paper is higher.With the increase of water supply temperature,the payback period of investment in Lanzhou is smaller than that in Xi’an.As the incremental cost of the project increases and the water supply temperature rises,the cost of the corresponding phase change heat storage device also increases.The cost of the phase change heat storage device in Lanzhou increases even more,which can be used as a guide for the selection of the phase change heat storage device in actual engineering projects. |
