The zone hot water radiator model calculates the convective and radiant heat transfer from the device to the people and the surfaces within a zone so that surface heat balances can take into account the radiant heat transfer to the surfaces and thus enhance the accuracy of thermal comfort predictions within the space. The component is controlled to meet any remaining zone load not met by other zone equipment.
This is a read-only label that is automatically generated by the software and which incorporates the name of the zone in which the radiator is located.
There are 3 ways to define the heating capacity of the unit as selected from the following list of options:
This autosizable field defines the convective electric nominal heating capacity (in W or Btu/h). It is only available when the Heating design capacity method is set to 1-Design capacity.
Enter the heating capacity per unit floor area (in W/m2 or W/ft2) of the unit. This data is only available when the Heating design capacity method is 2-Capacity per floor area.
The program calculates the heating capacity from floor area of the zone served by the unit and the heating capacity per unit floor area value specified here.
Enter the heating capacity as a fraction of the autosized heating capacity for convective electric baseboard unit. This data is only available when the Heating design capacity method is 3-Fraction of autosized capacity. EnergyPlus calculates the heating capacity from the design autosized heating capacity and this fraction. The default value is 1.0.
This is the maximum water volumetric flow rate in (m3/sec or gal/min). It can be auto-sized by EnergyPlus.
This is the rated average water temperature for the radiator (in °C or °F). It typically ranges from 65°C to 115°C and the lowest allowable temperature is 32°C. The default value is 75°C. This information should be provided by manufacturer’s literature.
This is the rated standard water flow rate (in kg/s or lb/s) which should be provided by manufacturer’s literature. It is used by the manufacturers when determining the rated capacity (see Rated capacity below). The default value is 0.063kg/s.
Note: If you are setting a heating design capacity (above) you must enter a corresponding Rated water mass flow rate here to ensure that you obtain the expected capacity in the simulation. Leaving this setting in default state could result in significant under or oversizing of the radiator. You can obtain maximum flow rates from the EnergyPlus Summary output as a guide.
This field specifies what fraction of the power input to the radiator is actually transferred to the space as radiant heat. The fraction should be between 0 and 1. This is the portion of the total power that is modelled as radiation. The portion that is radiant heat transfer from the radiator is distributed to people and specific surfaces using the remaining fields.
This field specifies the fraction of radiant portion of heat transfer to the zone from the radiator that is incident directly on people within the space. This has an impact on the predicted thermal comfort of the zone occupants. Note that although this energy is “radiant” it is actually modeled in the zone heat balance as convective energy (like an internal gain). The basic assumption here is that most radiant energy falling on people will most likely be re-released to the zone air by convection. This is a simplification of reality, but it maintains the overall energy balance.
Note: The remaining fraction is divided across all of the surfaces of the zone in which the radiator is located.
This is the schedule that determines whether or not the component is available for each timestep of the simulation. A schedule value greater than 0 (usually 1 is used) indicates that the unit can be on during the timestep. A value less than or equal to 0 (usually 0 is used) denotes that the unit must be off for the timestep.
This is the control tolerance for the radiator output. The radiator is controlled by matching the radiator output to the zone demand. The model must be numerically inverted to obtain a specified output. The convergence tolerance is the error tolerance used to terminate the numerical inversion procedure. Basically this is the fraction:
The default is 0.001.