recordDXCoil

Information

This record declares the performance data for the air source DX cooling coil model. The performance data are structured as follows:

  nSta      - Number of stages. Set to 1 for single speed coil,
              2 for dual-speed (or dual stage coils), etc.
  minSpeRat - Minimum speed ratio, used only for variable speed coils.
  sta       - Array of records with one performance curve for each stage,
              as described below.

Each element of the array per has the following data.

  spe       - Rotational speed for the respective stage.
              (This is only used for variable speed coils to interpolate for
              intermediate speeds).
  nomVal    - Nominal performance values for the respective stage. Data of the
              nomVal record are
     Q_flow_nominal - Total rate of cooling at nominal conditions.
     COP_nominal    - Coefficient of performance at nominal conditions.
     SHR_nominal    - Sensible heat ratio at nominal conditions.

     m_flow_nominal - Evaporator air mass flow rate at nominal conditions.
     TEvaIn_nominal    - Evaporator air inlet wet-bulb temperature at nominal conditions.
     TConIn_nominal    - Condenser air inlet temperature at nominal conditions
                         (for evaporative coils, use wet bulb, otherwise use dry bulb
                         temperature).
     phiIn_nominal  - Relative humidity at evaporator inlet at nominal conditions.
     p_nominal      - Atmospheric pressure at nominal conditions.

     tWet           - Time until moisture drips from coil when coil is switched on
     gamma          - Ratio of evaporation heat transfer divided by latent
                      heat transfer at nominal condition.

  per       - Array of records with one performance curve for the respective
              stage of the coil. That is, the performance curves will be used
              in conjunction with the nominal values defined in the record spe.
     capFunT  - Coefficients of biquadratic polynomial for cooling capacity
                as a function of temperature.
     capFunFF - Polynomial coefficients for cooling capacity
                as a function of the mass flow fraction.
     EIRFunT  - Coefficients of biquadratic polynomial for EIR as a function of temperature.
     EIRFunFF - Polynomial coefficients for EIR
                as a function of the mass flow fraction.
     [TConInMin, TConInMax] - Minimum and maximum condenser air inlet temperatures
                 for which the performance curves are valid.
                 Outside this range, they will be linearly extrapolated.
     [TEvaInMin, TEvaInMax] - Minimum and maximum evaporator air inlet temperatures
                 for which the performance curves are valid.
                 Outside this range, they will be linearly extrapolated.
     [ffMin, ffMax] - Minimum and maximum air mass flow fraction (relative to m_flow_nominal)
                 for which the performance curves are valid.
                 Outside this range, they will be linearly extrapolated.

The data used to develop the performance curves capFunT and EIRFunT should represent performance when the cooling coil is wet, i.e., the coil providing sensible cooling and at least some dehumidification. Performance data when the cooling coil is dry (i.e., not providing any dehumidification) should not be included when developing these modifier curves. The DX coil model automatically detects and adjusts for dry coil conditions by evaluating the performance curves for the wet bulb and dry bulb temperatures at the evaporator inlet, and then selecting the corresponding performance. The selection of the corresponding performance is described and implemented in Buildings.Fluid.DXSystems.Cooling.BaseClasses.DryWetSelector.

The parameters tWet and gamma characterize the amount of moisture that evaporates from the coil surface into the air stream when the coil is wet and switched off. For an examplanation of the parameters, see Buildings.Fluid.DXSystems.Cooling.BaseClasses.Evaporation.

There can be an arbitrary number of polynomial coefficients for the record capFunFF and EIRFunFF. However, if a coil has multiple stages, then each stage must declare the same amount of polynomial coefficients. For example, if a quadratic function is used for stage one, then stage two must also use a quadratic function.

Parameters

Revisions

• April 6, 2024, by Karthik Devaprasad:
  Replaced unused parameter names with correct parameter pairs for curve limit definitions in the documentation.
• April 4, 2023, by Xing Lu and Karthik Devaprasad:
  Updated record class name from DXCoil to CoolingCoil.
• May 30, 2014, by Michael Wetter:
  Removed undesirable annotation Evaluate=true.
• September 25, 2012 by Michael Wetter:
  Added documentation.
• July 23, 2012 by Kaustubh Phalak:
  First implementation.