Perform Hydronics What-ifs and Simulations

FOR HEATING contractors, sizing and specifying equipment for hydronic systems often entails time-consuming calculations, especially when trying out variables. Working with hand calculations takes a lot of time, or it results in best guesstimates when you’re figuring out what flow rate a given circulator would produce, how to compensate for temperature drops along a piping loop of fin-tube baseboard, how changing pipe size affects flow rate in a circuit or how big the expansion tank should be.

Computerized number crunching can lighten the workload and help assure a job is properly sized for the structure.

The recently updated Windows-based Hydronics Design Studio Professional Version, from Appropriate Designs (www.hydronicpros.com, $285, limited trial version downloadable free at Web site) is a 10-module heat-load estimating program that provides the ability to ask what-if questions and simulate and analyze a system very quickly.

While it does not design a hydronic system, the program, geared to residential and light commercial contractors, enables fast and accurate sizing of system components, instantly performing numerous types of calculations that would take hours to do by hand without the user needing to know the advanced engineering math behind them.

Generally, contractors start the estimating process with the Room Heat Load Estimator module, which calculates the design heating load of user-specified rooms, including the load due to air leakage.

The contractor defines the room by inputting the size of the walls, height of ceilings, area of windows and doors, and outside design temperature and selecting R-values for materials. The module combines calculated total heat loss with a total derived from the Basement Heat Load Estimator, which determines heat loss of a basement based on height of back fill, insulation and construction materials. A listing of rooms with their associated heat losses can be generated quickly.

The total heating load of the building is also automatically tabulated and displayed as rooms are added, deleted or modified. The building heat-loss information can be stored at any time for later reference.

The contractor then proceeds to use other modules to simulate thermal and hydraulic performance of various intended systems, such as baseboard or radiant floor.

The heart of the software is the Hydronic Circuit Simulator, which simulates thermal and hydraulic performance of user-defined circuits, including radiant panels. Featuring databases of more than 100 brand name circulators (most models available from U.S. and Canadian manufacturers, 2 hp or less), piping, fittings, valves, fluids and other components, the module enables configuration of either a series or a parallel piping circuit with up to 12 branches.

Users can define the circuits by length of pipe, size of pipe, type of pipe, type of fluid running in the pipe, circulator manufacturer and operating temperature. The module will perform all the hydraulic and thermal calculations, including those that indicate flow rates in different parts of the circuit. Modifications such as temperature, flow rates and valve settings are easy to enact and recalculate. The program, in effect, mimics the performance of any given inputted system, allowing trying before “buying” and eliminating the risk of installing hardware that may not perform as expected.

Other modules, which share information, assuring accuracy and eliminating the effort of duplicate entry, provide additional simulating and sizing models.

The Series Baseboard Simulator, which includes complete databases of baseboards, circulators, piping, fluids and other components, evaluates performance of circuits containing up to 12 baseboards and up to 10 zones. The baseboard database includes all manufacturers with I=B=R certification as compiled by the Hydronics Institute Division of the Gas Appliance Manufacturers Association. The simulator will build a perimeter circuit of all rooms in a house, using data from the room heat-load estimator module.

The Pipe Sizer helps to determine required size of copper, PEX and PEX-AL-PEX tubing, based on specified flow or required rate of heat transfer. The module calculates the head loss, pressure drop and Reynolds number of the flow for the selected pipe size and also calculates and displays the flow velocities in all other sizes of the pipe type selected for comparison.

The Fluids Properties Calculator calculates the density, specific heat and viscosity of water, propylene glycol, and ethylene glycol and determines the alpha value of the fluid. Concentration values of the glycols can vary between 20% and 50%. This versatility enables a contractor to take a water-based system and recalculate it with the appropriate level of antifreeze for a snow-melt job, for example.

Other modules include the Heating Cost Estimator, which estimates annual space heating cost for several fuels and efficiencies for quick comparisons, and provides weather data for hundreds of U.S. and Canadian locales; the Expansion Tank Sizer, which can calculate required expansion tank volume over a wide range of conditions; the Hydraulic Resistance Calculator; and the Pipe Heat Loss Estimator.

William and Patti Feldman provide Web content for companies and write for magazines, trade associations, building product manufacturers and other companies on a broad range of topics. They can be reached at [email protected].