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The HVAC Engineering Book’s modules are:
- COMFORT ― for predicting thermal comfort at various indoor conditions
- DESIGN LOADS ― for calculating building loads and sizing central and terminal equipment
- AIRFLOW ― for calculating duct and air diffusion systems
- WATERFLOW ― for calculating piping systems
- PSYCHROMETRICS ― for calculating moist air properties.
Many existing HVAC computer programs conceal their algorithms and interim calculation results, often causing misinterpretation of inputs and outputs. To avoid these shortcomings, the modules are organized in interlinked tabs placed in the order of the design progress. The tabs expose virtually each step of the calculations accompanied by formulae descriptions.
The modules allow for design of air-conditioining systems supplying constant or variable air volume to up to 50 comfort zones.
The modules coded in Inch-Pound units were compared with the examples in the source ASHRAE handbooks and standards and the simulation by software tool HAP-4.3 (Carrier Inc) performed for the sample building. The validation results presented in the guide reveal expected deviations of the calculation outputs against the ASHRAE sources.
Consulting engineers have the option of integrating the modules with their existing spreadsheets in a customized system for time-effective production of HVAC projects. For example, a change in a window area input automatically changes the ductwork pressure loss, the air diffuser throw, etc.
The COMFORT module predicts an “average” feeling of comfort in spaces with radiant heating or cooling panels and other special indoor conditions. It allows for alternative selection of the design comfort parameters: panel radiant temperature, the indoor air's temperature, relative humidity, and velocity. The calculation algorithm adopts the method outlined in Standard 52-2004 “Thermal Environmental Conditions for Human Occupancy.” The first step calculates Mean Room Radiant Temperature and thermal asymmetry. The second step calculates Predicted Mean Vote to quantify the comfort level at a selected set of comfort parameters. The module validation was based on comparison with the sample calculations provided by the standard.
The DESIGN LOADS module includes the following interlinked tabs:
- The Spaces tab populates the space’s geometry, occupancy, and heat gain sources
- The Climate tab summarizes the design climatic data required for load calculations
- The Envelope tab calculates the heat transfer coefficients and other characteristics of the envelope. The calculated characteristics are compared with the allowances from the Energy Standard 90.1-2007
- The Zoning tab groups the spaces into comfort zones and systems
- The System Configuration tab configures the air-conditioning systems with different design concepts
- The Space Ventilation tab calculates the space ventilation air volume rates
- The Space Heat Loss tab provides the space heat loss breakdowns
- A set of Cooling Loads tabs calculate the cooling loads from walls, windows, and other heat sources and summarize the space cooling load breakdowns
- The Zone Airflow Rates tab calculates the zone design airflow rates
- The System Airflow Rates tab calculates the system design airflow rates
- The System Ventilation Rates tab calculates the outdoor air volume requirements at the air-handlinging unit's air-intake
- The Fans tab summarizes the supply, return, and exhaust fan data from other tabs and checks compliance with Energy Standard 90.1-2007
- The Cooling Coil tab calculates the cooling coil capacity
- The Preheat Coil tab calculates the preheat coil and humidifier capacities
- The Reheat Coils tab summarizes the zone winter and summer reheat loads
- The Space Heating Units tab summarizes the perimeter heating unit design loads
- The Building Heating Loads tab provides the building heating load breakdown, ensuring that no loads are overlooked or double counted
- The Reports tab presents the tabs' calculation outputs in printable reports.
The AIRFLOW module includes two tabs:
- The Diffusers tab calculates required throws for selected types of air terminals based on the Air Diffusion Performance Index method
- The Ducts tab sizes duct systems of different shape and material carrying air at a selected temperature. The user selects the duct section sizes based on the calculated friction loss rates and air velocities. The tab allows to calculate the system pressure loss.
The WATERFLOW module includes three tabs:
The Pipe Load Calculator tab assists in calculation of design water flow rates in the sections of piping systems. The water flow rates are proportional to the design thermal loads of the radiators, heating coils, and other equipment served by the pipe sections. Calculation of the water flow rates is tedious and error prone work, especially for extensive reverse return systems. The tab automatically distributes the water flow rates (expressed in energy units) amongst the system's pipe sections for both direct and reverse return systems.
The Piping tab uses the water flow rates calculated by the Pipe Load Calculator tab to size the system's sections at a selected pipe material and water temperature. The user selects the pipe section diameters based on the calculated friction loss rates and water velocities. This tab calculates the section- and system-related pressure losses and water contents.
- The Expansion Tank tab calculates the expansion tank volume required, based on the water contents from the Piping tab.
