Figure 300-59 shows heat rejection rates for forced liquid cooling of cast iron cylinders. Cast steel or forged steel cylinders have lower heat rejection rates, mainly because the walls are thicker, and the jacketed areas are smaller. The following values may be used for estimating purposes for average conditions:
• cast iron cylinders 700 BTU/Bhp-hr
• cast steel cylinders 250 BTU/Bhp-hr
• forged steel cylinders 200 BTU/Bhp-hr
The coolant inlet temperature should be at least 10°F above the suction temperature to prevent condensation. The coolant temperature-rise across each cylinder should be at least 10°F, but no more than 20°F.
The following relationships should be treated as guidelines. They will not provide exact answers for all applications. Consult the vendor if it is necessary to know the discharge temperature more accurately.
The average gas and coolant temperatures affect the actual discharge temperature of cylinders with forced cooling. If the average gas temperature less the average coolant temperature is between 50°F – 60°F, the discharge temperature should be close to that predicted by Equation 300-25. For other temperature differentials, refer to Figure 300-60 to determine an estimate of the deviation from adiabatic discharge temperature.
Two other types of cooling systems are applied to cylinders: thermosyphon and no coolant circulation (static filled jackets). Refer to API 618 for criteria to apply these systems. Figure 300-61 gives temperature relationships for these systems.