Section 4: SIZING AND LOAD ESTIMATION
- Chapter 1: ASHRAE STANDARD METHODS
- Chapter 2: THE BUILDING COMFORT ANALYSIS PROGRAM METHODOLOGY
Several standard methods are available to size heating and cooling systems for specific applications. All methods follow a fairly regimented procedure that involves identifying the indoor design conditions, the outdoor design conditions, and the heat losses and gains through the structure. Once these parameters are determined, the next step requires information about the internal heating and cooling loads (e.g., people, computers, and lights), followed finally by the selection of the heating and cooling equipment.
The ASHRAE standard methods for sizing heating and cooling systems first specify the indoor dry-bulb temperature and the design outdoor temperature. The heat transfer rates into and out of the occupied space are calculated from the methods described in Sec. 2of this Handbook. The infiltration rates are also calculated, along with any heat gains due to lights, people, and other equipment. The final balance equation is developed from the conservation of energy equation as:
Note that the heat transfer rates may be functions of the indoor temperature, the outdoor temperature, and the insulation values of the walls, floors, ceilings, windows, and doors as shown in Sec. 2. The variable is the amount of energy that must be added to the room to maintain the indoor dry-bulb temperature at the design condition.
This chapter provides an overview of the standard methods used by practicing engineers to specify and size heating and cooling systems for occupied spaces. Additional information that can be used...