Coil:Heating:WaterToAirHeatPump:EquationFit
Coil:Heating:WaterToAirHeatPump:ParameterEstimation
Used in:
- Zone Water To Air Heat Pump
- Unitary Water To Air Heat Pump AHU
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Coil:Heating:WaterToAirHeatPump:EquationFit Coil:Heating:WaterToAirHeatPump:ParameterEstimation |
Used in:
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The Water to Air Heat Pump Heating Coil provides access to the EnergyPlus Equation fit (Curve fit) and Parameter Estimation models.
Equation Fit: The Equation Fit Water to Air heat pump heating coil is a simple curve-fit model that requires coefficients generated from heat pump catalog data to model performance. The model resembles a black box with no use of heat transfer equations. A detailed description of the equation-fit model is available in the following reference: Tang,C. C. 2005. Modeling Packaged Heat Pumps in Quasi-Steady State Energy Simulation Program. M.S. Thesis. Department of Mechanical and Aerospace Engineering, Oklahoma State University. It is also downloadable from www.hvac.okstate.edu.
DesignBuilder v2026.1 and later only: Parameter Estimation: The Parameter Estimation Water to Air heat pump Heating coil is a deterministic model that requires parameters to describe the operating conditions of the heat pump’s components. The parameters are generated from the manufacturer catalog data using multi-variable optimisation method. The parameters required for WatertoAirHP heating coil are similar to WatertoAirHP cooling except the source side outside heat transfer coefficient parameter is not required for heating.
A unique auto-assigned name identifying name for the coil. Any reference to this coil by another object (typically a Zone Water To Air Heat Pump or a Unitary Water To Air Heat Pump AHU) will use this name.
Two types of coil are available:
1-Equation Fit - a simple curve-fit model that requires coefficients generated from heat pump catalog data to model performance.
2-Parameter Estimation - a deterministic model that requires parameters to describe the operating conditions of the heat pump’s components. The parameters are generated from the manufacturer catalog data using multi-variable optimisation method.
Note: The Coil type selected here must match the setting on the paired Water-to-Air Heat Pump Cooling Coil.
The following settings are required when the Coil type is set to 1-Equation Fit.
This numeric field contains the rated volumetric air flow rate on the load side of the heat pump (in m3/s or ft3). This field is autosizable.
This numeric field contains the rated volumetric water flow rate on the source side of the heat pump (in m3/s or gal/min). This field is autosizable.
This numeric field contains the gross heating capacity of the heat pump at the rated condition (in W or Btu/hr). The gross heating capacity should not account for the effect of supply air fan heat. This field is autosizable.
This numeric field contains the gross rated heating coefficient of performance of the heat pump. The gross rated COP of the heat pump should not account for the effect of supply air fan heat.
This numeric field contains the ratio of rated heating capacity to the rated cooling capacity. It is used to determine the autosized rated heating capacity from the rated cooling capacity. It is also used to determine the autosized rated cooling capacity when peak heating loads are dominating during sizing calculations. If both this object’s and its associated cooling coil’s capacity are provided by the user, this field not used.
Typical values for this field depend on the application in which the coils are used. Some suggested values are 1.23 for water loop applications, 0.89 for ground water applications, and 0.76 for ground loop applications (source: 2021 AHRI directory).
This setting contains the entering water temperature at which the coil capacity, COP and power are rated at. As such, the coil’s COP should be entered at this temperature. The default value is 20°C (rating temperature for water loop water-to-air heat pumps in ISO-13256-1-1998).
This setting contains the entering air dry-bulb temperature at which the coil capacity, COP and power are rated at. As such, the coil’s COP should be entered at this temperature. The default value is 20°C (rated temperature for water loop water-to-air heat pumps in ISO-13256-1-1998).
Select a Quad Linear Performance Curve for the heat pump capacity. The Single Speed Equation-Fit Model for Unitary Water-To-Air Heat Pump under the Air System Compound Component Groups in the Engineering Reference document contains more explanation regarding these coefficients.
Select a Quad Linear Performance Curve for the heat pump power consumption. The Single Speed Equation-Fit Model for Unitary Water-To-Air Heat Pump under the Air System Compound Component Groups in the Engineering Reference document contains more explanation regarding this.
The following settings are required when the Coil type is set to 1-Parameter Estimation. DesignBuilder v2026.1 and later only.