scope:

This paper shows how air-to-air heat and enera system design problems can be formulated for a simple HVAC conjguration andsolved for the least life-cycle cost system while still retaining a small payback period. Mathematical expressions anddesign tables arepresented to facilitate the design process. The design process is illustratedfor the city of Chicago where both large heating and cooling loads occur in HVAC applications. The example design problem presented shows that paybackperiods of less than one year are often achieved for energy wheels and sometimes for sensible heat exchangers. The life-cycle cost savings for auxilialy heating and cooling ventilation air jar exceeds the capital cost of the energy exchanger (sensible or total), even when only a ten-year life cycle is considered.