What happens to the suction and discharge pressure when heat load on an evaporator increases?

When the heat load on an evaporator increases, both the suction and discharge pressure tend to increase due to the enhanced thermal activity and the corresponding changes in refrigerant conditions within the heat pump system.

As the heat load on the evaporator increases, it requires more refrigerant to absorb heat. This leads to an increase in the evaporator's pressure as the refrigerant is vaporized more efficiently at higher heat loads. As the evaporator pressure rises, the suction pressure also increases because the low side of the system is directly dependent on the evaporator pressure.

Moreover, as more heat is absorbed and converted into vapor, it also impacts the discharge side. The increased vapor flow from the evaporator puts more demand on the compressor to move this vapor through the system. This results in a rise in the discharge pressure because the compressor must work harder to expel the vapor at a higher pressure to maintain efficient system operation.

In summary, both the suction and discharge pressures increase due to the combined effect of the increased heat load on the evaporator and the subsequent increase in refrigerant vapor flow throughout the heat pump system.