Q1: Air refrigeration cycle is used in the air crafts, because of

ANS:C - its low unit weight per ton of refrigeration.

Air refrigeration cycles are used in aircraft primarily because of the low unit weight per ton of refrigeration. Explanation:

1. Low Unit Weight per Ton of Refrigeration:
   • Aircraft have strict limitations on weight due to considerations of fuel efficiency, payload capacity, and structural integrity.
   • Air refrigeration cycles offer a significant advantage in terms of weight efficiency compared to other refrigeration methods.
   • The refrigerant in an air refrigeration cycle is the ambient air itself, which is abundant and does not need to be carried onboard as a separate fluid or refrigerant. This eliminates the need for heavy refrigerant storage tanks or systems.
   • The absence of heavy refrigerant components results in a lower unit weight per unit of cooling capacity (ton of refrigeration), making air refrigeration systems highly suitable for aircraft applications.
2. Other Considerations:
   • While low temperature encountered at high altitudes is a factor in aircraft refrigeration, the primary consideration for aircraft refrigeration systems is often the weight efficiency.
   • Air refrigeration cycles generally have lower coefficients of performance (COP) compared to vapor compression cycles used in ground-based refrigeration systems.
   • The heat transfer rate of air refrigeration systems is influenced by various factors, including the design of the heat exchangers and the airflow dynamics, but it is not necessarily higher than other refrigeration methods.
3. Advantages of Air Refrigeration in Aircraft:
   • Apart from weight considerations, air refrigeration cycles offer other advantages in aircraft applications, such as simplicity, reliability, and the ability to operate over a wide range of ambient temperatures.
   • They also eliminate the need for carrying and replenishing refrigerants, reducing maintenance requirements and potential environmental hazards associated with refrigerant leaks.

In summary, air refrigeration cycles are favored in aircraft primarily due to their low unit weight per ton of refrigeration, which is essential for meeting weight restrictions and optimizing aircraft performance. Other factors, such as simplicity and reliability, also contribute to their suitability for aircraft applications.