Introduction

Heating load must be calculated for peak building heating demand. For example, let's assume that the coldest days (peak heating demand) and hours during the heating season are five consecutive days in the month of January from 5:00 AM to 9:00 AM. In this case, the heating boiler or the HVAC unit must be sized to handle the heating load on these coldest days even though during the other months and days the heating load is much lower. It should be noted also during the coldest days and hours the following assumptions are very accurate:

1. The variation in outdoor temperature is very minimal and is nearly constant.

2. Solar heat gain is not a big factor, so it can be ignored.

3. Heat gain from internal sources can reasonably be ignored.

4. Heat storage of the building structure can be ignored.

With the above reasonable assumptions we can conclude that the heat transfer process for the heating load calculations is steady state. Of course it should be noted that for the annual energy consumption analysis of the building, the variation in outdoor temperature, solar heat gain, heat storage of the structure, and heat gain from internal sources such as lights, people, and appliances cannot be ignored and must be included in the analysis. In this case, the heat transfer process is instantaneous and the transfer function method described in the 2001 ASHRAE Fundamental Handbook should be used for the analysis.

In this book we present the procedure for carrying...