Numerical And Experimental Study Of A Novel Heat Recovery Ventilator With Heat Pump System

The application of fresh air equipment in building HVAC systems is one of the main technical means to improve indoor air quality.Due to the additional heat and cold load generated by the introduction of the fresh air,using the exhaust air heat recovery unit to precool or preheat the fresh air for energy saving is considered to be a feasible way to reduce the energy consumption of the HVAC systems.The fresh air equipment with heat pump system has the characteristics that the air outlet parameters are controllable and not affected by geographical conditions.Besides,it can be used as an independent cool/heat source and is flexible in application,which makes it has broad application prospects.However,according to the existing research,because of the low operating efficiency,it is not able to meet the requirements of resident users who are relatively sensitive to operating costs,which is become the biggest obstacle to the application of these equipment.Therefore,this study presents a novel two-level exhaust air heat pump ventilator which enhanced by indirect evaporative cooling method.Moreover,experimental and numerical study of the ventilator is included in this study.The main work of this study are as follows:Firstly,based on the previous research on the exhaust air heat pump system and the indirect evaporative cooling heat recovery,the novel ventilator which uses the advantage of both two methods was proposed and the prototype was designed and experimentally tested.During the test,the operating characteristics of the prototype under the full-year variable operating conditions were tested in detail.In particular,in summer conditions tests,the experiment included four operating modes.The experimental results shows that,the standard operating conditions in summer,the EER of the ventilator reaches 5.12,which is much higher than that of the exhaust air pump system in the existing research.Then,the mathematical model of the main components such like evaporative cooling heat recovery heat exchanger and the exhaust air heat pump system is established in this study.The calculation of the mathematical model is performed in the Matlab 2017 a.The simulation model is modeled according to the characteristics of each module and the heat transfer characteristics,that make it can simulate the operating characteristics of the ventilator in different operating environments under various operating conditions.And based on the detailed mathematical model of each component,the heat exchange process for each component can be studied using the simulation platform.The accuracy of the simulation platform was also verified and calibrated by the data from experimental studies.Besides,the operating characteristics of the ventilator under different indoor and outdoor environmental conditions were simulated by the simulation platform.The study focused on the effects of fresh air temperature and humidity,degree,exhaust air temperature and humidity,and the change of fresh air exhaust air volume on the performance of the ventilator in winter and summer heating and cooling conditions.Furthermore,except of the traditional energy analysis,the study also analyzes and optimizes the heat and moisture exchange and energy transfer and conversion processes occurring in the ventilator with the derivation of the second law of thermodynamics.In this process,the shape of the indirect evaporative cooling heat recovery heat plate exchanger and the overall operation flow of the ventilator have become the main research objects.The conclusion reveals the source of the main energy loss in the fresh air main engine,and establishes the theoretical basis and direction guidance for further improving its efficiency.Finally,this paper establishes a building dynamic simulation platform based on the joint platform of Trnsys and Matlab.The simulation of the annual operation of the heating system of the fresh air main unit combined with the conventional heat pump air conditioner in the small civil building is carried out,and the annual energy consumption under different control strategies is compared.The situation gives a more energy-efficient year-round operational strategy.Compared with two regular operating strategies,this strategy saves 14.4% and 10.1% respectively.On this basis,this study uses the simulation platform to simulate the performance of the system under different meteorological conditions in different cities,and compares it with two conventional systems.