Coupling a horizontal heat exchanger with an all in one machine for heating and cooling a single-family house in a mild climate

Heat, ventilation and air conditioning (HVAC) systems are considered of great importance in the building sector, as they represent a significant part of the energy demand in buildings. Moreover, they are deeply related to indoor environment quality, which strongly affects occupants’ quality of life. This paper presents the analysis on a compact all-in-one and plug-and-play machine providing heating, cooling and mechanical controlled ventilation in a low energy residential building. In particular, the system is composed by a heat pump connected to a heat recovery unit which can pre-heat the fresh air and contribute to the DHW production. In the present work an additional heat exchanger set in the building’s basement has been included into the system, in order to pre-heat or pre-cool the outdoor air before entering the heat recovery unit. The compact energy system has been mathematically modelled and its operations have been monitored in a real building recently constructed. The model of the system has indeed been implemented on the basis of a report test on the operating performance of the machine provided by the constructor, and the tuning has been realized according to the real operation tests, properly done for this analysis. The real case study is a low energy building located in Udine (North-East of Italy), inhabited by four people and with total floor area of 240 m2 . The simulated annual energy performance of the all-in-one machine have been obtained and the layouts of the system with and without the ground heat exchangers have been compared. Dynamic simulations have been carried out to examine the indoor thermal comfort for both the configurations, in order to verify the possibility to employ the basement heat exchanger for improving, besides the energy performances, also the indoor environmental quality.