Which of the problems listed would cause the discharge pressure and temperature of an R-134a air-cooled refrigeration unit to increase above normal for existing conditions?
• Refrigeration cycle high-side vs low-side pressures for R-134a systems • How condenser performance (heat rejection) affects discharge pressure and temperature • Effects of expansion valve or suction gas changes on compressor discharge conditions
• Ask what must physically happen in the system to make the compressor work against a higher pressure and produce hotter discharge gas under the SAME load and ambient conditions. • Consider which option directly reduces the system’s ability to reject heat to the surroundings, forcing pressures and temperatures higher. • Think about which options mainly affect evaporator/suction conditions instead of condenser/discharge conditions, and whether that would raise or lower discharge pressure.
• Identify which component directly controls condensing pressure and temperature in an air‑cooled system. • For each choice, trace the effect on condenser heat transfer, not just on flow rate or safety devices. • Eliminate options that would tend to lower head pressure or only affect when the unit shuts off, rather than actually changing the pressure/temperature produced.
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