Cascade Heater

Under construction.

Performance

The Cascade Heater component comprises of a combination of 3 “Heater” type components. Thereby the performance calcs associated with Cascade Heaters are dsitrubuted amongst both performance_cascade_heater and performance_heater calculations.

The following performance calculations are available on cascade heater instances:

Calculation Reference Output Tags
TTD ASME PTC 12.1 .ttd.use
DCA ASME PTC 12.1 .dca.use
UTF   .util.use
Temp Rise   .c1.dT.use
Desuperheater - Heat Transfer   .desuperheater.c1.dQ.use
Desuperheater - Heat Transfer Coefficient   .desuperheater.heatTransferCoefficient.use
Condenser - Heat Transfer   .condenser.c1.dQ.use
Condenser - Heat Transfer Coefficient   .condenser.heatTransferCoefficient.use
Drain Cooler - Heat Transfer   .drainCooler.c1.dQ.use
Drain Cooler - Heat Transfer Coefficient   .drainCooler.heatTransferCoefficient.use
  • TTD - Terminal Termperature Difference
  • LMTD - Log Mean Temperature Difference
  • DCA - Drain Cooler Approach Temperature
  • UTF - Utilisation Factor

Calculations

Temperature Rise

The temperature rise is defined as:

$$T_{r} = T_{fwout} - T_{fwin}$$

Where:

  • $T_{r}$ = Temperature rise $(^{o}C)$
  • $T_{fwout}$ = Feedwater outlet temperature $(^{o}C)$
  • $T_{fwin}$ = Feedwater inlet temperature $(^{o}C)$

In CAS terms:

$$.c1.dT.use = .c1out.prop.temp.use - .c1in.prop.temp.use$$

Heat Transfer

The heat transfer is defined as:

$$Q_{htr} = Q_{fwout } - Q_{fwin}$$

Where:

  • $Q_{htr}$ = Heat transfer (kW)
  • $Q_{fwout }$ = Feedwater outlet heatflow (kW)
  • $Q_{fwin}$ = Feedwater inlet heat flow (kW)

In CAS terms:

$$c1.dQ.use - c1out.energyFlow.use - c1in.energyFlow.use$$

Log Mean Temperature Difference

The log mean temperature describes the mean temperature difference between cooling water and condensing steam (HEI Standard for Closed Feedwater Heaters section 1.7).

$$LMTD = \frac{T_{fwout} - T_{fwin}}{In\left ( \frac{T_{satsteamin} - T_{fwin}}{T_{satsteamin} - T_{fwout}} \right )}$$

Where:

  • $T_{satsteamin}$ = saturation temperature heater shell pressure $(^{o}C)$

In CAS terms:

$$.LMTD.use = \frac{.c1.dT.use}{In\left ( \frac {.c2in.prop.satTemp.use - .c1in.prop.temp.use}{.c2in.prop.satTemp.use - .c1out.prop.temp.use} \right )}$$

Heat Transfer Coefficient

$$HTC = \frac{Q}{LMTD}$$

Where:

  • $HTC$ = Heat transfer coefficient of heater (kW/$^{o}C$)
  • $Q$ = Heat transferred from feedwater (kW)
  • $LMTD$ = Log mean temperature difference of heater $(^{o}C)$

In CAS terms:

$$.heatTransferCoefficient.use = \frac{.c1.dQ.use}{.lmtd.use}$$

Terminal Temperature Difference

$$TTD = T_{extsteam} - T_{fwout}$$

Where:

  • $TTD$ = Heat terminal temperature difference $(^{o}C)$
  • $T_{extsteam}$ = saturation temperature of extraction steam $(^{o}C)$

In CAS terms:

$$.ttd.use = .c2in.prop.satTemp.use - .c1out.prop.temp.use$$

Drain Cooler Approach

$$DCA = T_{drainate} - T_{fwin}$$

Where:

  • $T_{drainate}$ = Heater drainate temperature $(^{o}C)$

In CAS terms:

$$.dca.use = .c2out.prop.temp.use - .c1in.prop.temp.use$$

Heater Utility Factor

$$UTILITY = \frac{T_{rdiff}}{T_{rdesign}}$$

Where:

  • $T_{rdiff}$ = Feedwater temperature rise $(^{o}C)$
  • $T_{rdesign}$ = Feedwater temperature rise at design conditions $(^{o}C)$

In CAS terms:

$$.utilityFactor.use = \frac{.c1.dT.use}{.c1.dT.design}$$

Contact us

Phone

+617 3229 3333

Address

28E Gladstone Rd
Brisbane, QLD 4101
Australia