tailieunhanh - HVAC Systems Design Handbook part 3

All solutions to engineering problems start with a calculation or estimation of the duty which must be met (., quantifying the problem). The purpose of heating and cooling load calculations, then, is to quantify the heating and/or cooling loads in the space(s) to be conditioned. Rough estimates of load may be made during the concept design phase. | Source HVAC Systems Design Handbook Chapter 3 Design Procedures Part 1 Load Calculations Introduction All solutions to engineering problems start with a calculation or estimation of the duty which must be met . quantifying the problem . The purpose of heating and cooling load calculations then is to quantify the heating and or cooling loads in the space s to be conditioned. Rough estimates of load may be made during the concept design phase. During design development and final design it is essential to make orderly detailed and well-documented load calculations because these form the basis for equipment selection duct and piping design and psychrometric analysis. Today s energy and building codes also require detailed documentation to prove compliance. The necessity for order and documentation cannot be overemphasized. While it may sometimes seem unnecessary to list all criteria and assumptions these data are invaluable when changes or questions arise sometimes months or years after the design is completed. This chapter refers to a great many data tables from the ASHRAE Handbook. Many of these tables require several pages in the 81 2-in by 11-in format of the Handbook and are presented here in abstract form. For the complete tables refer to the Handbook. Use of Computers Current practice is to use computers for load calculations. Many load calculation programs exist with varying degrees of complexity and accuracy. Most can be run on small personal computers while some 25 Downloaded from Digital Engineering Library @ McGraw-Hill Copyright 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. Design Procedures Part 1 26 Chapter Three require large computer systems. There are several important things to consider when a computer is used 1. The program to be used must be credible and well documented. Any automated procedure should be capable of being supported in