Heating Load Calculations
MECH 8250 – Building Systems Module 1 - Heating Load Calculations Module 1 Heating Load Calculations The amount of heat is required for the building heating system to maintain a balance of the building heat loss. The amount of heat and moisture are gained from the building internal and external heat sources that is required to be removed by the building cooling system. Both heating and cooling loads form the basis in designing the HVAC systems for the building and occupied spaces to achieve both thermal comfort and good indoor air quality in the building. In addition, the calculated heating and cooling load can be used to provide estimate of energy consumption of building. Page 1 of 33
Heating load
Cooling Load -
Applications
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Note: Heating load relates to the building heat loss Cooling load relates to the building heat gain
Methods for Estimating Loads Accepted methods to calculate the heating and cooling loads are documented in the ASHRAE Handbook of Fundamentals. The earlier methods (before 1993) are simple and can be performed manually. The later methods after 1993 have become more complicated that it is only practical with the use of computer programs. However, improvement of the earlier method can be made using the Excel spreadsheet. Accuracy and precision of the heating and cooling loads calculations do not depend exactly on the manual or computational methods. This is due to the fact that building elements and contents are complex assemblies and it is difficult to model the actual heat flow paths through 100 percents of all the building assembly. So, it is more important for designers and engineers to appreciate the relative accuracy of the calculated building heating and cooling loads when designing the HVAC systems.
Critical Conditions for Designs Critical design conditions for the heating system will occur in winter and at a time when the building has minimal heat gains from radiant solar energy, the lights, appliance or people
Heating load
Cooling Load -
Applications
-
Note: Heating load relates to the building heat loss Cooling load relates to the building heat gain
Methods for Estimating Loads Accepted methods to calculate the heating and cooling loads are documented in the ASHRAE Handbook of Fundamentals. The earlier methods (before 1993) are simple and can be performed manually. The later methods after 1993 have become more complicated that it is only practical with the use of computer programs. However, improvement of the earlier method can be made using the Excel spreadsheet. Accuracy and precision of the heating and cooling loads calculations do not depend exactly on the manual or computational methods. This is due to the fact that building elements and contents are complex assemblies and it is difficult to model the actual heat flow paths through 100 percents of all the building assembly. So, it is more important for designers and engineers to appreciate the relative accuracy of the calculated building heating and cooling loads when designing the HVAC systems.
Critical Conditions for Designs Critical design conditions for the heating system will occur in winter and at a time when the building has minimal heat gains from radiant solar energy, the lights, appliance or people
References: 1. ASHRAE handbook 2005 – Fundamental, Atlanta, GA 30329. 2. Janis, R. Richard & Tao, K.Y. William (2008), Mechanical and Electrical Systems in Buildings, 4th Edition, Pearson/Prentice Hall.