Condenser Total Heat of Rejection
The load the condenser or cooling tower must shed, which the refrigeration side never computes.
Example
You enter
- Evaporator capacity (tons, or Btu/h if unit set to 0) 5
- Capacity unit 1
- Coefficient of performance COP 2.4
You get
- Compressor work 25000 Btu/h
- Total heat of rejection 85000
- Thr (ton) 7.08
- Heat-rejection factor 1.417 (THR / Q_evap)
Checked against published worked examples from: ACHR News (J. Marchese).
Details, formula, and sources
ScopeTHR = Q_evap (1 + 1/COP), the evaporator load plus the compressor work. A 5-ton system at COP 2.4 rejects 85,000 Btu/h (7.08 tons) - a 1.42 heat-rejection factor, 42% more than it absorbs; drop to COP 1.5 and it climbs to 100,000 Btu/h, so a struggling system overloads its own condenser and drives head pressure higher still. No heat-recovery split; hermetic / suction-cooled basis (an open-drive motor rejects its losses to the room). An engineering aid; the rated heat-of-rejection data govern.
Formula or tableQ_btuh = (unit == tons) ? Q x 12,000 : Q; W_comp = Q_btuh/COP; THR = Q_btuh (1 + 1/COP); factor = 1 + 1/COP; THR_tons = THR/12,000.
Source and editionThe condenser total heat of rejection THR = Q_evap + W_comp = Q_evap (1 + 1/COP), a standard refrigeration-cycle result, by name.
Free accessThe total-heat-of-rejection relation is a public refrigeration-cycle result; the ASHRAE Handbook covers condenser sizing.
What governsEstimate. AHJ and licensed professional govern.
API field namesq_evap, unit_tons, cop, w_comp_btuh, thr_btuh, thr_tons, factor
- Heat of rejection THR = Q_evap (1 + 1/COP), the evaporator load plus the compressor workenergy balance
- Rejection factor 1 + 1/COP, about 1.25 for comfort cooling, higher at lower COPrefrigeration practice
- No heat recovery full rejection at the condenser; no desuperheater split or external motor heatscope of this tile