What is the necessary adjustment to reduce the pressure in an absorption refrigerating plant?

In an absorption refrigerating plant, reducing the pressure is often accomplished by adjusting the flow of steam to the generator. The generator is responsible for providing the heat necessary for the refrigerant to evaporate and through its absorption cycle. When the flow of steam to the generator is reduced, it leads to lower temperatures and consequently decreases the pressure within the system. This adjustment is critical because maintaining the correct pressure is essential for the absorption cycle to function efficiently.

Increasing the flow of refrigerant, adjusting the expansion valve, or increasing the drum temperature do not directly address the need to reduce pressure within the system. These actions could potentially lead to increased pressure or disrupt the balance necessary for effective operation. Thus, reducing the flow of steam ensures the absorption system operates under the desired pressure conditions, making this choice the correct answer.