THE FUNCTIONAL BASIS OF STEADY-STATE THERMAL-ENERGY USE IN AIR-SIDE HVAC EQUIPMENT

A proper understanding of the functional basis of energy use in reside nces has been crucial in spurring energy conservation in such building stock. In commercial buildings, however, such understanding is lackin g, partly because there are numerous possible HVAC system types and co ntrol strategies, and partly because the detailed algorithms available to simulate energy use in various types of HVAC systems provide littl e insight into identifying ways of saving energy in existing buildings . The objective of this paper is to derive closed-form steady-state fu nctional relations for air-side cooling and heating thermal energy use for four of the most widespread HVAC system types, namely terminal re heat and dual-duct, both under constant air volume and under variable air volume operation. Expressions are derived for hourly energy use as a function of climatic variables, building characteristics, and syste m parameters. The effects of economizer cycle and deck reset schedules are also treated. The expressions derived could be utilized to develo p functionally accurate regression models of monitored energy use for retrofit savings determination and to ascertain whether the HVAC syste m is operating properly, as well as for parameter estimation from eith er short-term or long-term monitoring and for sensitivity analyses of how various physical and operating parameters affect energy use.