Heating, Ventilation and Air-Conditioning

Abstract

Heating, Ventilation and Air-conditioning, or simply HVAC, can be considered one of the most important services in modern buildings. In the tropical countries, external temperature can be around 35°C on average with a relative humidity up to 90% – 100% in summer. In countries near to the poles, outdoor temperature can be as low — 30°C in winter or even lower. Human beings just cannot work efficiently under such an environment. The major contribution of HVAC systems to the mankind is the fine control to arrive at a comfortable indoor environment for people to work and live. Furthermore, a controlled environment is often a necessity for industrial manufacturing plants. According to ASHRAE, thermal comfort is that condition of mind that expresses satisfaction with the thermal environment. Comfort also includes behavioral actions initiated by the conscious mind and guided by thermal and moisture sensations to reduce discomfort. This book is about building systems and hence, the focus is placed upon comfort air-conditioning while industrial air-conditioning is outside our scope. In this chapter, the concept of human comfort, the basic structure and different types of HVAC systems will be discussed. As most of the control technologies discussed in this book are on cooling, the emphasis has not been placed upon heating and ventilation.