Recent energy simulation model enhancements for radiant systems

The HVAC industry and the simulation technology that is used to inform it are constantly changing to address new challenges and improved technology and strategies. Sometimes, simulation technology, for a variety of reasons, has not kept up with developments in the field. This has been the case with the low temperature radiant system model in EnergyPlus. Since its inclusion in the program during the early 2000s, the model for low temperature radiant systems has seen a few improvements, but there have been no additions to the modeling capabilities for over 10 years. With recent work on the program, several new features and enhancements have been made to increase the usability of the program as architects and engineers seek to better model building energy usage. Recent improvements to the model in EnergyPlus include the addition of surface and internal temperature controls, the enhancement of setpoint interpretation, the implementation of on–off and running mean outside air temperature controls, the definition of a time delay between changes from heating to cooling or vice versa, the description of multi-zone radiant systems, and the inclusion of a new heat exchange algorithm between the fluid and the radiant system itself. All these new features are described and demonstrated through simulation results.