Development of a mathematical model for control optimisation of a domestic nh3 heat pump

Abstract

Consulta en la Biblioteca ETSI Industriales (7568)

[EN] In residential applications, a geothermal ammonia (NH3) small-scale heat pump is used in combination with a domestic hot water storage tank, and the performance of this system is affected significantly not only by the space heating needs but also by hourly domestic hot water consumption and temperature distribution in the storage tank. In this paper, the performance of a NH3 heat pump water heating system is analysed by numerical simulation. A simulation model is created based on thermodynamic equations and the values of model parameters are estimated based on measured data for existing devices. The corresponding computer program is then written using MATLAB 6.5, and used to study the performance and system working. In this model, the control of the heat pump is done by controlling either Domestic Hot Water (DHW) outlet temperature or Space Heating Water (SHW) one. Then the calculated performance is compared for every simulation, changing the working parameters in order to find the optimum control temperature. In fact it is also shown that the temperatures of both SHW and DHW have influence on how the system works, as well as the power and performance of the heat pump. Moreover we have also studied the variation of the working parameters with the seasonal changes of outdoor temperature and the heat pump capacity. Finally the simulation model is validated using heat balances in each system part along the 24 h period. We conclude that only one control strategy is possible: SHW as primary control then DHW as secondary control, for verifying the PR 255 DHW requirements.