Buildings.Fluid.DXSystems.BaseClasses

Package with base classes for DX cooling coil model

Information

This package contains base classes that are used to construct the models in Buildings.Fluid.DXSystems.

Extends from Modelica.Icons.BasesPackage (Icon for packages containing base classes).

Package Content

Name	Description
CapacityAirSource	Calculates cooling capacity at given temperature and flow fraction for air source coils
DryCoil	Calculates dry coil condition
Examples	Package with examples of base class components for DX cooling coil model

Buildings.Fluid.DXSystems.BaseClasses.CapacityAirSource

Calculates cooling capacity at given temperature and flow fraction for air source coils

Buildings.Fluid.DXSystems.BaseClasses.CapacityAirSource

Information

This model calculates cooling capacity and EIR for air source DX coils in off-designed conditions based on performance modifers calculated in partial model Buildings.Fluid.DXSystems.Cooling.BaseClasses.PartialCapacity.

Cooling capacity

The cooling capacity modifiers are multiplied with nominal cooling capacity to obtain the cooling capacity of the coil at given inlet temperatures and mass flow rate as

Q̇(θ_e,in, θ_c,in, ff) = cap_θ(θ_e,in, θ_c,in) cap_FF(ff) Q̇_nom,

where θ_e,in is the evaporator inlet temperature and θ_c,in is the condenser inlet temperature in degrees Celsius. θ_e,in is the dry-bulb temperature if the coil is dry, or the wet-bulb temperature if the coil is wet. cap_θ(θ_e,in, θ_c,in) is cooling capacity modifier as a function of temperature. cap_FF(ff) is cooling capacity modifier as a function of nomalized mass flowrate at the evaporator.

Energy Input Ratio (EIR)

The Energy Input Ratio (EIR) is the inverse of the Coefficient of Performance (COP). Similar to the cooling rate, the EIR of the coil is the product of a function that takes into account changes in condenser and evaporator inlet temperatures, and changes in mass flow rate. The EIR is computed as

EIR(θ_e,in, θ_c,in, ff) = EIR_θ(θ_e,in, θ_c,in) EIR_FF(ff) ⁄ COP_nominal

Extends from Buildings.Fluid.DXSystems.Cooling.BaseClasses.PartialCapacity (Calculates performance curve value at given temperature and mass flow rate).

Parameters

Type	Name	Default	Description
Boolean	use_mCon_flow	false	Set to true to enable connector for the condenser mass flow rate
Integer	nSta		Number of coil stages (not counting the off stage)
Stage	sta[nSta]	redeclare parameter Building...	Performance data for this stage
Initialization
Real	cap_T.start[nSta]	1	Cooling capacity modification factor as a function of temperature
Real	cap_FF.start[nSta]	1	Cooling capacity modification factor as a function of flow fraction
Real	EIR_T.start[nSta]	1	EIR modification factor as a function of temperature
Real	EIR_FF.start[nSta]	1	EIR modification factor as a function of flow fraction
Real	corFac.start[nSta]	1	Correction factor that is one inside the valid flow fraction, and attains zero below the valid flow fraction

Connectors

Type	Name	Description
input IntegerInput	stage	Stage of coil, or 0/1 for variable-speed coil
input RealInput	TConIn	Temperature of air entering the condenser coil [K]
input RealInput	m_flow	Air mass flow rate at the evaporator [kg/s]
input RealInput	TEvaIn	Temperature of air entering the evaporator (wet bulb for wet coil and dry bulb for dry coil) [K]
input RealInput	mCon_flow	Water mass flow rate at the condenser [kg/s]
output RealOutput	Q_flow[nSta]	Total cooling capacity [W]
output RealOutput	EIR[nSta]	Energy Input Ratio

Modelica definition

block CapacityAirSource "Calculates cooling capacity at given temperature and flow fraction for air source coils" extends Buildings.Fluid.DXSystems.Cooling.BaseClasses.PartialCapacity( use_mCon_flow=false); equation if stage > 0 then for iSta in 1:nSta loop Q_flow[iSta] = corFac[iSta]*cap_T[iSta]*cap_FF[iSta]*sta[iSta].nomVal.Q_flow_nominal; EIR[iSta] = corFac[iSta]*EIR_T[iSta]*EIR_FF[iSta]/sta[iSta].nomVal.COP_nominal; end for; else //cooling coil off Q_flow = fill(0, nSta); EIR = fill(0, nSta); end if; end CapacityAirSource;

Buildings.Fluid.DXSystems.BaseClasses.DryCoil

Calculates dry coil condition

Buildings.Fluid.DXSystems.BaseClasses.DryCoil

Information

This block calculates the rate of heating/cooling and the coil surface condition under the assumption that the coil is dry. The heat transfer calculations are done in Buildings.Fluid.DXSystems.BaseClasses.CapacityAirSource.

For a similar model that is used to compute the wet coil conditions, see Buildings.Fluid.DXSystems.Cooling.BaseClasses.WetCoil.

Extends from Buildings.Fluid.DXSystems.Cooling.BaseClasses.PartialCoilCondition (Partial block for dry and wet coil conditions).

Parameters

Type	Name	Default	Description
DXCoil	datCoi	redeclare parameter Building...	Performance data
Boolean	use_mCon_flow		Set to true to enable connector for the condenser mass flow rate
Boolean	variableSpeedCoil		Flag, set to true for coil with variable speed
CapacityAirSource	coiCap	redeclare Buildings.Fluid.DX...	Performance data
replaceable package Medium		Modelica.Media.Interfaces.Pa...	Medium model

Connectors

Type	Name	Description
input IntegerInput	stage	Stage of coil, or 0/1 for variable-speed coil
input RealInput	speRat	Speed ratio
input RealInput	m_flow	Air mass flow rate
input RealInput	TEvaIn	Temperature of air entering the cooling coil
input RealInput	TConIn	Outside air dry bulb temperature for an air cooled condenser or wetbulb temperature for an evaporative cooled condenser [K]
output RealOutput	EIR	Energy Input Ratio
output RealOutput	Q_flow	Total cooling capacity [W]
input RealInput	mCon_flow	Water mass flow rate at condensers for water source DX units
replaceable package Medium		Medium model

Modelica definition

model DryCoil "Calculates dry coil condition" extends Buildings.Fluid.DXSystems.Cooling.BaseClasses.PartialCoilCondition; replaceable package Medium = Modelica.Media.Interfaces.PartialCondensingGases "Medium model"; equation connect(TEvaIn,coiCap.TEvaIn); connect(mCon_flow,coiCap.mCon_flow); end DryCoil;