# SIZING HEATING EQUIPMENT

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## SIZING HEATING EQUIPMENT

Specific heat is significant because the amount of heat requiredÂ to change the temperatures of different substances is used toÂ size equipment. Recall the example of the house and furnaceÂ earlier in this unit. The following example shows how thisÂ would be applied in practice. A manufacturing company mayÂ need to buy a piece of heating equipment to heat steel before itÂ can be machined. The steel may be stored outside in the cold atÂ 0Â°F and need preheating before machining. The desired metalÂ temperature for the machining is 70Â°F. How much heat mustÂ be added to the steel if the plant wants to machine 1000 lb/h?Â The steel is coming into the plant at a fixed rate ofÂ 1000 lb/h, and heat has to be added at a steady rate toÂ stay ahead of production. Figure 1.15 gives a specific heatÂ of 0.116 Btu/lb/Â°F for steel. This means that 0.116 Btu ofÂ heat energy must be added to 1 lb of steel to raise its temperature
1Â°F.

Q = Â Weight * Specific Heat * Temperature Difference

where Q = quantity of heat needed. Substituting in the
formula,

we get:
Q = 1000 lb/h * 0.116 Btu/lb/Â°F * 70Â°F

Q = 8120 Btu/h required to heat the steel for machining.

The previous example has some known values and anÂ unknown value to be found. The known information is usedÂ to find the unknown value with the help of the formula. TheÂ formula can be used when adding heat or removing heatÂ and is often used in heat-load calculations for sizing bothÂ heating and cooling equipment.

Copied fromÂ REFRIGERATION &Â AIR CONDITIONINGÂ TECHNOLOGY byÂ WILLIAM C. WHITMAN,Â WILLIAM M. JOHNSON,Â JOHN A. TOMCZYK andÂ EUGENE SILBERSTEIN

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