System-Level Heat Exchanger (TL-G)

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A heat exchanger based on performance data between heat-conducting liquid and gas networks.

blockType: EngeeFluids.HeatExchangers.SystemLevel.ThermalLiquidGas

Path in the library:

/Physical Modeling/Fluids/Heat Exchangers/Thermal Liquid - Gas/System-Level Heat Exchanger (TL-G)

Description

Block System-Level Heat Exchanger (TL-G) simulates a heat exchanger based on performance data between heat-conducting liquid and gas networks.

The unit uses performance data from the technical data sheet of the heat exchanger, rather than the detailed geometry of the heat exchanger. You can adjust the size and performance of the heat exchanger during the design process or model heat exchangers with non-standard geometries. This unit can also be used to simulate heat exchangers with a certain level of performance at an early stage of design, when detailed geometry data is not yet available.

The parameterization of the unit is performed in accordance with the nominal operating conditions. The unit determines the parameters of the heat exchanger in accordance with the set capacity under nominal operating conditions in steady state.

This block is similar to the block Heat Exchanger (G-TL), but uses a different parameterization model. The comparison of the two blocks is shown in the table.

Heat Exchanger (G-TL)	System-Level Heat Exchanger (TL-G)
The unit parameters depend on the geometry of the heat exchanger	The parameters of the unit depend on the performance and operating conditions
The geometry of the heat exchanger may be limited by the available geometry parameters.	The model does not depend on the specific geometry of the heat exchanger
You can customize the unit to meet different performance requirements by changing geometric parameters such as rib sizes and tube lengths.	You can customize the unit to meet different performance requirements by directly specifying the required heat consumption and mass values.
You can choose a direct-flow, countercurrent, shell-and-tube, or cross-flow coolant flow pattern.	You can choose a direct-flow, countercurrent, or cross-flow coolant flow pattern under nominal operating conditions, which will help determine the size.
Predictably accurate results over a wide range of operating conditions, depending on the applicability of the E-NTU equations and correlations of heat transfer coefficients.	Very accurate results near the specified operating conditions; accuracy may decrease with significant distance from the specified operating conditions
Heat transfer calculations take into account temperature changes along the flow path using the E-NTU model	Heat transfer calculations approximate the temperature change along the flow path, dividing it into three segments

Heat Exchanger (G-TL)

System-Level Heat Exchanger (TL-G)

The unit parameters depend on the geometry of the heat exchanger

The parameters of the unit depend on the performance and operating conditions

The geometry of the heat exchanger may be limited by the available geometry parameters.

The model does not depend on the specific geometry of the heat exchanger

You can customize the unit to meet different performance requirements by changing geometric parameters such as rib sizes and tube lengths.

You can customize the unit to meet different performance requirements by directly specifying the required heat consumption and mass values.

You can choose a direct-flow, countercurrent, shell-and-tube, or cross-flow coolant flow pattern.

You can choose a direct-flow, countercurrent, or cross-flow coolant flow pattern under nominal operating conditions, which will help determine the size.

Predictably accurate results over a wide range of operating conditions, depending on the applicability of the E-NTU equations and correlations of heat transfer coefficients.

Very accurate results near the specified operating conditions; accuracy may decrease with significant distance from the specified operating conditions

Heat transfer calculations take into account temperature changes along the flow path using the E-NTU model

Heat transfer calculations approximate the temperature change along the flow path, dividing it into three segments

Heat transfer

The block divides the gas flow and the heat-conducting liquid flow in the block into three segments of the same size. The unit calculates the heat transfer between the heat carriers in each segment. For simplicity, the equations in this section are given for a single segment.

If you uncheck the box Wall thermal mass, then the heat balance in the heat exchanger will be

where

— heat flow from the wall, which is the heat transfer surface, to the gas in the segment; — heat flow from the wall to the heat-conducting liquid in the segment.

If you check the box Wall thermal mass, then the heat balance in the heat exchanger will be

where

— wall mass;
— specific heat capacity of the wall;
— number of segments;
— average wall temperature in the segment;
— the time.

The heat flow from the wall to the gas in the segment is

where

— heat transfer capacity for gas in the segment;
— the average gas temperature in the segment.

The heat flow from the wall to the heat-conducting liquid in the segment is

where

— heat transfer capacity for a heat-conducting liquid in the segment;
— the average temperature of the heat-conducting liquid in the segment.

Correlation of heat transfer of a heat-conducting liquid

The thermal conductivity on the side of the heat exchanger in contact with the heat-conducting liquid is

where

, , — correlation coefficients of the Nusselt number; these coefficients are the parameters of the block in the parameter group Correlation Coefficients;
— average Reynolds number for the segment;
— the average Prandtl number for the segment;
— average thermal conductivity for the segment;
— the scale factor of the geometry for the heat-conducting fluid side of the heat exchanger. The unit calculates the scale factor of the geometry so that the total heat transfer across all segments corresponds to the specified performance under nominal operating conditions.

The average Reynolds number is

where

— mass flow through the segment;
— average dynamic viscosity for the segment;
— arbitrary reference diameter;
— an arbitrary reference area of the flow section.

Members and included in this equation is only for calculating units of measurement to make dimensionless. Values and arbitrary, because the calculation overrides these values.

Correlation of gas heat transfer

The thermal conductivity on the side of the heat exchanger in contact with the gas is

where

, , — correlation coefficients of the Nusselt number; these coefficients are the parameters of the block in the parameter group Correlation Coefficients;
— average Reynolds number for the segment;
— the average Prandtl number for the segment;
— average thermal conductivity for the segment;
— the scale factor of the geometry for the gas side of the heat exchanger. The unit calculates the scale factor of the geometry so that the total heat transfer across all segments corresponds to the specified performance under nominal operating conditions.

The average Reynolds number is

where

— mass flow through the segment;
— average dynamic viscosity for the segment;
— arbitrary reference diameter;
— an arbitrary reference area of the flow section.

Members and included in this equation is only for calculating units of measurement to make dimensionless. Values and arbitrary, because the calculation overrides these values.

Pressure loss

The pressure losses on the side of the heat-conducting liquid are determined as follows

where

and — pressure in ports A1 and B1, respectively;
— the internal pressure of the heat-conducting liquid at which the unit calculates heat transfer;
and — mass expenses via ports A1 and B1, respectively;
— the average density of the heat-conducting liquid in all segments;
— threshold mass flow rate in laminar mode, approximately equal to 1e−4 the nominal mass flow rate. The unit calculates the pressure loss coefficient so that the difference it corresponded to the nominal pressure loss at the nominal mass flow rate.

The pressure losses on the gas side are determined as follows

where

and — pressure in ports A1 and B1, respectively;
— the internal gas pressure at which the unit calculates heat transfer;
and — mass expenses via ports A1 and B1, respectively;
— average gas density across all segments;
— threshold mass flow rate in laminar mode, approximately equal to 1e−4 the nominal mass flow rate. The unit calculates the pressure loss coefficient so that the difference it corresponded to the nominal pressure loss at the nominal mass flow rate.

Conservation of mass and energy of a thermally conductive liquid

The mass conservation equation for the entire flow of a thermally conductive liquid has the form

where

— partial derivative of density with respect to pressure for a segment;
— partial derivative of density with respect to temperature for a segment;
— temperature for the segment;
— the total volume of the heat-conducting liquid.

Summation is performed for all segments.

Although the unit divides both coolant streams into For calculating the heat transfer segment, it is assumed that all segments are under the same internal pressure . Therefore, it is not taken into account when summing.

The energy conservation equation for each segment has the form

where

— the partial derivative of the specific internal energy in terms of pressure for the segment;
— partial derivative of the specific internal energy with respect to temperature for the segment;
— the total mass of the heat-conducting liquid;
and — mass expenses to and from the segment;
and — energy consumption in and out of the segment.

The block assumes that the mass expenses between the segments are linearly distributed between the values and .

Conservation of gas mass and energy

The mass conservation equation for the entire gas flow has the form

where

— partial derivative of density with respect to pressure for a segment;
— partial derivative of density with respect to temperature for a segment;
— temperature for the segment;
— the total volume of gas.

Summation is performed for all segments.

Although the block divides the gas flow into For calculating the heat transfer segment, it is assumed that all segments are under the same internal pressure . Therefore, it is not taken into account when summing.

The energy conservation equation for each segment has the form

where

— partial derivative of the specific internal energy in terms of pressure for the segment;
— partial derivative of the specific internal energy with respect to temperature for the segment;
— total mass of gas;
and — mass expenses to and from the segment;
and — energy consumption in and out of the segment.

The block assumes that the mass expenses between the segments are linearly distributed between the values and .

Ports

Conserving

# A1 — port for heat-conducting liquid
heat-conducting liquid

Details

An input or output non-directional port connected to a heat-conducting fluid network.

Program usage name

thermal_liquid_port_a1

# B1 — port for heat-conducting liquid
heat-conducting liquid

Details

An input or output non-directional port connected to a heat-conducting fluid network.

Program usage name

thermal_liquid_port_b1

# A2 — gas port
gas

Details

An input or output non-directional port connected to the gas network.

Program usage name

gas_port_a2

# B2 — gas port
gas

Details

An input or output non-directional port connected to the gas network.

Program usage name

gas_port_b2

Output

# Q1 — the rate of heat transfer to a heat-conducting liquid, W
scalar

Details

The rate of heat transfer to a heat-conducting liquid, returned as a scalar signal, in Watts. The scalar signals on ports Q1 and Q2 are usually equal in magnitude and have the opposite sign. However, if you check the box Wall thermal mass These two signals may have different meanings, since the wall can absorb and give off part of the transmitted heat.

Data types	`Float64`
Complex numbers support	No

# Q2 — heat transfer rate to gas, W
scalar

Details

The rate of heat transfer to the gas, returned as a scalar signal, in Watts. The scalar signals on ports Q1 and Q2 are usually equal in magnitude and have the opposite sign. However, if you check the box Wall thermal mass These two signals may have different meanings, since the wall can absorb and give off part of the transmitted heat.

Data types	`Float64`
Complex numbers support	No

Parameters

Configuration

# Flow arrangement at nominal operating conditions — flow diagram of heat carriers under nominal operating conditions
Parallel flow - Both fluids flow from A to B | Counter flow - Thermal Liquid 1 flows from A to B, Gas 2 flows from B to A | Cross flow - Both fluids flow from A to B

Details

Flow diagram of heat transfer fluids between the sides of the heat exchanger under nominal operating conditions. Available coolant flow patterns:

Counter flow - Thermal Liquid 1 flows from A to B, Gas 2 flows from B to A — the streams move parallel to each other in opposite directions;
Parallel flow - Both fluids flow from A to B — the streams are moving in the same direction;
Cross flow - Both fluids flow from A to B — the streams move perpendicular to each other.

The choice between direct current and counterflow affects how the unit determines the size of the heat exchanger. The counterflow setting is the most efficient and requires the smallest size to achieve the desired performance. Conversely, the direct flow is the least efficient and requires the largest size to achieve the desired performance.

The flow direction under nominal conditions (from A to B or from B to A) only affects the initialization of the model when the checkbox is selected. Initialize thermal liquid to nominal operating conditions or Initialize gas to nominal operating conditions. When setting different initial operating conditions, the flow directions may be different.

After the unit determines the size of the heat exchanger, this parameter does not affect how the unit calculates heat transfer during simulation. Instead, the heat transfer depends on the flow direction during the simulation. For example, if you set the parameter to direct flow, and set the model to work in counterflow, the heat transfer rate during the simulation will not match the set performance, even if the other boundary conditions are the same.

If you specify a cross flow, the unit will model the flow paths inside the heat exchanger as perpendicular, so the flow direction does not matter during the simulation.

Values	`Parallel flow - Both fluids flow from A to B` \| `Counter flow - Thermal Liquid 1 flows from A to B, Gas 2 flows from B to A` \| `Cross flow - Both fluids flow from A to B`
Default value	`Counter flow - Thermal Liquid 1 flows from A to B, Gas 2 flows from B to A`
Program usage name	`flow_arrangement_type`
Evaluatable	No

# Wall thermal mass — should the influence of thermal inertia on the heat transfer surface be taken into account

Details

Whether to take into account the influence of thermal inertia on the heat transfer surface. When this option is selected, the block adds additional dynamics to the simulation and increases the time to reach the steady state, but this parameter does not affect the results of the steady state simulation.

Default value	`false (switched off)`
Program usage name	`wall_thermal_mass`
Evaluatable	No

# Cross-sectional area at port A1 — cross-sectional area of the flow in the port A1
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the flow in the port A1 for a thermally conductive liquid.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area_a1`
Evaluatable	Yes

# Cross-sectional area at port B1 — cross-sectional area of the flow in the port B1
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the flow in the port B1 for a thermally conductive liquid.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area_b1`
Evaluatable	Yes

# Cross-sectional area at port A2 — cross-sectional area of the flow in the port A2
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the flow in the port A2 for gas.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area_a2`
Evaluatable	Yes

# Cross-sectional area at port B2 — cross-sectional area of the flow in the port B2
m^2 | um^2 | mm^2 | cm^2 | km^2 | in^2 | ft^2 | yd^2 | mi^2 | ha | ac

Details

The cross-sectional area of the flow in the port B2 for gas.

Units	`m^2` \| `um^2` \| `mm^2` \| `cm^2` \| `km^2` \| `in^2` \| `ft^2` \| `yd^2` \| `mi^2` \| `ha` \| `ac`
Default value	`0.01 m^2`
Program usage name	`port_area_b2`
Evaluatable	Yes

# Wall mass — wall mass
kg | mg | g | t | lbm | oz | slug

Details

The mass of the wall.

Dependencies

To use this option, check the box Wall thermal mass.

Units	`kg` \| `mg` \| `g` \| `t` \| `lbm` \| `oz` \| `slug`
Default value	`1.0 kg`
Program usage name	`wall_mass`
Evaluatable	Yes

Details

Specific heat capacity of the wall.

Dependencies

To use this option, check the box Wall thermal mass.

Units	`J/(kgK)` \| `kJ/(kgK)` \| `cal/(kgK)` \| `kcal/(kgK)` \| `cal/(gK)` \| `kcal/(gK)` \| `Btu_IT/(lbm*deltadegR)`
Default value	`490.0 J/(kg*K)`
Program usage name	`c_p_wall`
Evaluatable	Yes

# Initialize wall temperature to nominal operating conditions — wall temperature initialization option

Details

The option to initialize the wall temperature with nominal operating conditions or preset values. If this option is selected, the unit calculates the initial wall temperature based on the nominal operating conditions set for both sides of the heat carriers. If you uncheck this box, you can set the initial wall temperature directly using the parameter Initial wall temperature.

Dependencies

To use this option, check the box Wall thermal mass.

Default value	`true (switched on)`
Program usage name	`wall_nominal_initialization`
Evaluatable	No

Details

The initial temperature of the wall. If a scalar is set, then the block assumes that the initial wall temperature is uniform. If a two-element vector is specified, the block assumes that the initial wall temperature varies linearly between ports A1 and A2 and ports B1 and B2. The first element corresponds to the temperature in ports A1 and A2, and the second element corresponds to the temperature in ports B1 and B2.

Dependencies

To use this option, check the box Wall thermal mass and uncheck the box Initialize wall temperature to nominal operating conditions.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`[293.15] K`
Program usage name	`T_wall_start`
Evaluatable	Yes

Thermal Liquid 1

# Nominal operating condition — nominal operating condition
Heat transfer from Thermal Liquid 1 to Gas 2 | Heat transfer from Gas 2 to Thermal Liquid 1

Details

Nominal operating condition used for a heat-conducting fluid network:

Heat transfer from Thermal Liquid 1 to Gas 2 — the heat-conducting liquid cools, and the gas heats up;
Heat transfer from Gas 2 to Thermal Liquid 1 — the gas cools, and the heat-conducting liquid heats up.

This setting applies only to the parameters of the nominal operating conditions. This does not mean that during the simulation, heat transfer can only occur in the specified direction.

Values	`Heat transfer from Thermal Liquid 1 to Gas 2` \| `Heat transfer from Gas 2 to Thermal Liquid 1`
Default value	`Heat transfer from Thermal Liquid 1 to Gas 2`
Program usage name	`operating_condition_1`
Evaluatable	No

Details

Mass flow rate from port A1 to port B1 under nominal operating conditions.

Units	`kg/s` \| `kg/hr` \| `kg/min` \| `g/hr` \| `g/min` \| `g/s` \| `t/hr` \| `lbm/hr` \| `lbm/min` \| `lbm/s`
Default value	`0.1 kg/s`
Program usage name	`mdot_nominal_1`
Evaluatable	Yes

# Nominal pressure drop — pressure difference between the ports of the heat-conducting liquid under nominal operating conditions
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

Pressure difference between port A1 and port B1 under nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.01 MPa`
Program usage name	`delta_p_nominal_1`
Evaluatable	Yes

# Nominal inlet pressure — nominal pressure of the heat-conducting liquid at the inlet
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The pressure of the heat-conducting liquid at the inlet to the heat exchanger under nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.101325 MPa`
Program usage name	`p_inlet_nominal_1`
Evaluatable	Yes

Details

The temperature of the heat-conducting liquid at the inlet to the heat exchanger under nominal operating conditions.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`333.15 K`
Program usage name	`T_inlet_nominal_1`
Evaluatable	Yes

# Heat transfer capacity specification — the method of setting the heat exchanger performance
Rate of heat transfer | Outlet condition

Details

Determine the performance of a heat exchanger for a heat-conducting liquid under nominal operating conditions directly, by the rate of heat transfer, or indirectly, by the output parameters.

Values	`Rate of heat transfer` \| `Outlet condition`
Default value	`Rate of heat transfer`
Program usage name	`capacity_specification_1`
Evaluatable	No

# Nominal rate of heat transfer — heat transfer rate under nominal conditions
W | uW | mW | kW | MW | GW | V*A | HP_DIN

Details

The rate of heat transfer. Parameter Nominal operating condition defines the gas network from which and to which heat is transferred:

if for the parameter Nominal operating condition the value is set Heat transfer from Thermal Liquid 1 to Gas 2, this parameter determines the rate of heat transfer from the side of the heat-conducting liquid to the side of the gas under nominal operating conditions;
if for the parameter Nominal operating condition the value is set Heat transfer from Gas 2 to Thermal Liquid 1, then this parameter determines the rate of heat transfer from the gas side to the side of the heat-conducting liquid under nominal operating conditions.

Dependencies

To use this parameter, set for the parameter Heat transfer capacity specification meaning Rate of heat transfer.

Units	`W` \| `uW` \| `mW` \| `kW` \| `MW` \| `GW` \| `V*A` \| `HP_DIN`
Default value	`1.0 kW`
Program usage name	`Q_nominal`
Evaluatable	Yes

# Thermal liquid volume — volume of heat-conducting liquid
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3

Details

The total volume of heat-conducting liquid inside the heat exchanger.

Units	`m^3` \| `um^3` \| `mm^3` \| `cm^3` \| `km^3` \| `ml` \| `l` \| `gal` \| `igal` \| `in^3` \| `ft^3` \| `yd^3` \| `mi^3`
Default value	`0.001 m^3`
Program usage name	`V_thermal_liquid`
Evaluatable	Yes

# Initialize thermal liquid to nominal operating conditions — the option of initializing the heat-conducting liquid to the nominal conditions

Details

The option of initializing the heat-conducting liquid to the nominal operating conditions or set values. If this option is selected, the unit initializes the heat-conducting liquid to the rated operating conditions. If you uncheck this box, you can set the initial conditions directly using additional parameters.

Default value	`true (switched on)`
Program usage name	`nominal_initialization_1`
Evaluatable	No

# Initial thermal liquid pressure — the pressure of the heat-conducting liquid at the beginning of the simulation
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The pressure of the heat-conducting liquid at the beginning of the simulation.

Dependencies

To use this option, uncheck the box. Initialize thermal liquid to nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.101325 MPa`
Program usage name	`p_start_1`
Evaluatable	Yes

Details

The temperature of the heat-conducting liquid at the beginning of the simulation.

Dependencies

To use this option, uncheck the box. Initialize thermal liquid to nominal operating conditions.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`[293.15] K`
Program usage name	`T_start_1`
Evaluatable	Yes

Details

The temperature of the heat-conducting liquid at the outlet of the heat exchanger under nominal operating conditions.

Dependencies

To use this parameter, set for the parameter Heat transfer capacity specification meaning Outlet condition.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`323.15 K`
Program usage name	`T_outlet_nominal_1`
Evaluatable	Yes

Gas 2

Details

Mass flow rate from port A2 to port B2 under nominal operating conditions.

Units	`kg/s` \| `kg/hr` \| `kg/min` \| `g/hr` \| `g/min` \| `g/s` \| `t/hr` \| `lbm/hr` \| `lbm/min` \| `lbm/s`
Default value	`0.1 kg/s`
Program usage name	`mdot_nominal_2`
Evaluatable	Yes

# Nominal pressure drop — pressure difference between gas ports under nominal operating conditions
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

Pressure difference between port A2 and port B2 under nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.001 MPa`
Program usage name	`delta_p_nominal_2`
Evaluatable	Yes

# Nominal inlet pressure — nominal gas inlet pressure
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The gas pressure at the inlet to the heat exchanger under nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.101325 MPa`
Program usage name	`p_inlet_nominal_2`
Evaluatable	Yes

Details

The temperature of the gas at the inlet to the heat exchanger under nominal operating conditions.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`293.15 K`
Program usage name	`T_inlet_nominal_2`
Evaluatable	Yes

# Gas volume — gas volume
m^3 | um^3 | mm^3 | cm^3 | km^3 | ml | l | gal | igal | in^3 | ft^3 | yd^3 | mi^3

Details

The total volume of gas inside the heat exchanger.

Units	`m^3` \| `um^3` \| `mm^3` \| `cm^3` \| `km^3` \| `ml` \| `l` \| `gal` \| `igal` \| `in^3` \| `ft^3` \| `yd^3` \| `mi^3`
Default value	`0.1 m^3`
Program usage name	`V_gas`
Evaluatable	Yes

# Initialize gas to nominal operating conditions — gas initialization option to nominal conditions

Details

The option to initialize the gas to the nominal operating conditions or set values. If this option is selected, the unit initializes the gas to the rated operating conditions. If you uncheck this box, you can set the initial conditions directly using additional parameters.

Default value	`true (switched on)`
Program usage name	`nominal_initialization_2`
Evaluatable	No

# Initial gas pressure — gas pressure at the beginning of the simulation
Pa | uPa | hPa | kPa | MPa | GPa | kgf/m^2 | kgf/cm^2 | kgf/mm^2 | mbar | bar | kbar | atm | ksi | psi | mmHg | inHg

Details

The gas pressure at the beginning of the simulation.

Dependencies

To use this option, uncheck the box. Initialize gas to nominal operating conditions.

Units	`Pa` \| `uPa` \| `hPa` \| `kPa` \| `MPa` \| `GPa` \| `kgf/m^2` \| `kgf/cm^2` \| `kgf/mm^2` \| `mbar` \| `bar` \| `kbar` \| `atm` \| `ksi` \| `psi` \| `mmHg` \| `inHg`
Default value	`0.101325 MPa`
Program usage name	`p_start_2`
Evaluatable	Yes

Details

The temperature of the gas at the beginning of the simulation.

Dependencies

To use this option, uncheck the box. Initialize gas to nominal operating conditions.

Units	`K` \| `degC` \| `degF` \| `degR` \| `deltaK` \| `deltadegC` \| `deltadegF` \| `deltadegR`
Default value	`[293.15] K`
Program usage name	`T_start_2`
Evaluatable	Yes

Correlation Coefficients

# a in Nu = a*Re^b*Pr^c for thermal liquid — correlation coefficient for a thermally conductive liquid

Details

The proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for a thermally conductive liquid. The default value is based on the Colburn equation.

Default value	`0.023`
Program usage name	`a_const_1`
Evaluatable	Yes

# b in Nu = a*Re^b*Pr^c for thermal liquid — the exponent of the Reynolds number in correlation for a thermally conductive liquid

Details

The exponent of the Reynolds number in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for a thermally conductive liquid.

Default value	`0.8`
Program usage name	`b_const_1`
Evaluatable	Yes

# c in Nu = a*Re^b*Pr^c for thermal liquid — the exponent of the Prandtl number in correlation for a thermally conductive liquid

Details

The exponent of the Prandtl number in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for a thermally conductive liquid.

Default value	`0.33`
Program usage name	`c_const_1`
Evaluatable	Yes

# a in Nu = a*Re^b*Pr^c for gas — correlation coefficient for gas

Details

The proportionality constant in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for gas. The default value is based on the Colburn equation.

Default value	`0.023`
Program usage name	`a_const_2`
Evaluatable	Yes

# b in Nu = a*Re^b*Pr^c for gas — the exponent of the Reynolds number in the correlation for gas

Details

The exponent of the Reynolds number in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for gas. The default value is based on the Colburn equation.

Default value	`0.8`
Program usage name	`b_const_2`
Evaluatable	Yes

# c in Nu = a*Re^b*Pr^c for gas — the exponent of the Prandtl number in the correlation for gas

Details

The exponent of the Prandtl number in the correlation of the Nusselt number as a function of the Reynolds number and the Prandtl number for gas. The default value is based on the Colburn equation.

Default value	`0.33`
Program usage name	`c_const_2`
Evaluatable	Yes

Literature

Ashrae Handbook: Fundamentals. Atlanta: Ashrae, 2013.
Çengel, Yunus A. Heat and Mass Transfer: A Practical Approach. 3rd ed. McGraw-Hill Series in Mechanical Engineering. Boston: McGraw-Hill, 2007.
Mitchell, John W., and James E. Braun. Principles of Heating, Ventilation, and Air Conditioning in Buildings. Hoboken, NJ: Wiley, 2013.
Shah, R. K., and Dušan P. Sekulić. Fundamentals of Heat Exchanger Design. Hoboken, NJ: John Wiley & Sons, 2003.
Cavallini, Alberto, and Roberto Zecchin. «A Dimensionless Correlation for Heat Transfer in Forced Convection Condensation» In Proceeding of International Heat Transfer Conference 5, 309–313. Tokyo, Japan: Begellhouse, 1974. https://doi.org/10.1615/IHTC5.1220.