Heat recovery device in air-conditioning systems: Real cost saver or unnecessary investement

Nowadays an air-conditioning design engineer is faced with a challenging task to minimise energy consumption and capital costs. One of the most common solutions is to apply heat recovery device. However, simple application of heat recovery device may not always produce energy cost savings. Sometimes investment costs may overcome energy savings, and feed-back period may be longer than equipment lifetime. Usually, the conditions in which use of heat recovery device, in the air-conditioning systems, is economical, is not strictly and clearly defined. In this paper the appliance of heat recovery devices is discussed due to its economical approvement depending on the airflow, outside and inside air parameters, air conditioning system regime etc. From the point of view of the design engineer it is very important to define all parameters and their values which can influence possible choices on how to apply heat recovery devices. Those parameters concern the above mentioned data. The analysis procedure and algorithm that has been made in this paper cover is trying to define outside and inside air parameters which justify appliance of heat recovery devices. Special attention has been made to feed-back period as well to the regime of heat recovery devices. This paper then also summarises things that a design engineer should consider before he decides to apply some or other heat recovery device in order to achieve energy cost savings.