Improving IAQ and energy efficiency for buildings using vav air conditioning system based on fuzzy logic

Abstract

In recent years, in the quest focused about energy conservative building design, as a high efficiencyair conditioning scheme, the variable air volume (VAV) systems owe their growing popularity in heating,ventilation and air conditioning (HVAC) applications. This paper reports the simulation study toinvestigate the inherent operational characteristics of direct expansion (DX) VAV air conditioning (A/C)unit when the supply air fan and compressor speeds are varied based on the thermal load persisting inthe conditioned space. Based on the Matlab-Simulink environment, a new fuzzy based simulationmodel of the DX VAV system has been developed and the energy utilization of the air conditioningsystem is investigated by incorporating the concept of combined economizer cycle (EC) and demandcontrolled ventilation (DCV) techniques into the simulated model. Indoor air quality (IAQ) is addressedunder DCV and combined DCV-EC modes of ventilation. Simulation results obtained for the DX VAVA/C system are compared with the conventional constant air volume (CAV) system. The results inferthat the fuzzy control methodology and algorithm developed are feasible with a proper control of IAQbeing achieved. Variation of refrigerant mass flow rate corresponding to the variation of supply air flowrate is also investigated.