Improved heat recovery & air conditioning heat pump - Application in a northern hospital

This paper presents the configuration and some experimental performance data for an improved, custom designed heat recovery & air conditioning retrofitting system, developed for a hospital located in a Canadian cold-climate environment. The two-stage heat recovery system includes a conventional glycol heat exchanger and a prototype of a reversible air-to-air heat pump between the exhaust and the fresh air streams. The original feature of the heat pump consists mainly of two independent, parallel, vertical circuits, each including two identical, 9 and 16-ton in-tandem compressors, bi-directional liquid receivers, dedicated sub-coolers, supplementary condenser for extreme conditions, and a control strategy of compressors allowing for modulating the heating or cooling capacity, and to perform defrosting without inversion of the cycle. The system was monitored over a 12-month period, and the results focused on the thermodynamic parameters of the supplied and exhausted air, seasonal utilisation and performance factors, annual energy balances and savings, and pay-back period.