Heat recovery of decentralised façade units: A case study

Abstract

Indoor air quality affects the health of the premises' users and the efficiency of their work. Sealing the building envelope to reduce the demand for thermal energy reduces the number of air changes. One of the solutions that improve indoor air conditions is decentralised façade units to alternate air supply and exhaust. An important issue is the implementation of heat recovery in this type of solution, the aim of which is to reduce the energy consumption of ventilation and air conditioning systems. There is no description of research in the literature on the use of various methods of heat accumulation in façade units. The available descriptions are limited to aluminium, ceramics, and PCM. The novelty presented in this study is the use of gravel and gypsum as materials for storage in heat recovery exchangers.The objective of the article is to identify important factors influencing the efficiency of heat recovery, the parameters of air flowing through decentralised façade units, and the internal air temperature.The heat recovery exchanger located in a decentralised façade unit for alternating air supply and exhaust was analysed. Two exchanger filling configurations were tested: gravel and gypsum. Three variants of cycle length settings were analysed: 2 min, 6 min, and 10 min. Airflow, temperature before and after the heat recovery exchanger, and temperature inside and outside the room were measured.Research showed that the type of material that fills the heat recovery exchanger is more important than the duration of the cycle or airflow. The heat recovery efficiencies achieved for gypsum are 72 – 87 %, and for gravel 92 %. The material used and the setting do not affect the temperature values before the heat exchanger. The setting has no significant impact on the temperature after the heat recovery exchanger and on the indoor air temperature. In turn, the type of material significantly affects the values of these parameters.