# Standard Heater

Under construction.

## Performance

The following performance calculations are applied to all standard heater instances:

 Calculation Reference Output Tags LMTD (Log Mean Temperature Difference) ASME PTC 12.2,S 6.9 .LMTD.use Heat Transfer Coefficient .heatTransferCoefficient.use

## Calculations

LMTD (Co current)

$$LMTD = \frac{\left ( T_{gasin} - T_{steamin} \right ) - \left ( T_{gasout} - T_{steamout} \right )}{In \left ( \frac{T_{gasin} - T_{steamin}}{T_{gasout} - T_{steamout}} \right )}$$

Where:

• $T_{gasin}$ = Temperature of gas entering element $(^{o}C)$
• $T_{steamin}$ = Temperature of gas entering element $(^{o}C)$
• $T_{gasout}$ = Temperature of gas entering element $(^{o}C)$
• $T_{steamout}$ = Temperature of gas entering element $(^{o}C)$

In CAS terms:

$$element.lmtd.use = \frac{(ob.c2in.prop.temp.use - ob.c2in.prop.temp.use) - (ob.c2out.prop.temp.use - ob.c1in.prop.temp.use)}{In \left ( \frac{ob.c2in.prop.temp.use - ob.c1in.prop.temp.use}{ob.c2out.prop.temp.use - ob.c1out.prop.temp.use} \right )}$$

LMTD (Counter current)

$$LMTD = \frac{\left ( T_{gasin} - T_{steamin} \right ) - \left ( T_{gasout} - T_{steamout} \right )}{In \left ( \frac{T_{gasin} - T_{steamout}}{T_{gasout} - T_{steamin}} \right )}$$

In CAS terms:

$$element.lmtd.use = \frac{(ob.c2in.prop.temp.use - ob.c2in.prop.temp.use) - (ob.c2out.prop.temp.use - ob.c1in.prop.temp.use)}{In \left ( \frac{ob.c2in.prop.temp.use - ob.c1out.prop.temp.use}{ob.c2out.prop.temp.use - ob.c1in.prop.temp.use} \right )}$$

Heat Transfer Coefficient

The heat transfer coefficient is characterising parameter that incorporates the heat transfer coefficient and the geometry of the standard heater elements and is defined as:

$$HTC = \frac{Q}{\Delta T_{LM}}$$

Where:

• $HTC$ = Heat Transfer Coefficient (kW/$^{o}C$)
• $Q$ = Heat Flow from steam/gas (kW)
• $\Delta T_{LM}$ = Log Mean Temperature Difference $(^{o}C)$

In CAS terms:

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

A comparison of the actual and design values together with the components historical values, will determine whether the standard heater element is operating within an acceptable band from its design point.

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