What is the position of the suction and discharge valves when the piston is at top dead center?

When the piston is at top dead center (TDC) in a reciprocating compressor, both the suction and discharge valves are closed. At TDC, the piston has reached the highest point in its stroke, and there is no movement occurring in the cylinder to create a pressure differential that would allow for the opening of these valves.

This is a critical moment in the compression cycle. The suction valve needs to remain closed to prevent any backflow of refrigerant gas from the discharge side, ensuring that the compressor is ready to begin the intake cycle as the piston moves downward. Similarly, the discharge valve also remains closed to maintain pressure in the discharge line until the piston has completed its stroke and is ready to push the gas out.

Therefore, with both valves closed at this position, it ensures the proper function of the compressor cycle, maintaining the necessary conditions for efficient operation. Understanding this phase is essential for anyone working with refrigeration systems, as it relates to the timing and sequencing within the compression cycle.