Question

A rigid tank contains 5 kg of refrigerant-134a initially at 20°C and 160 kPa. The refrigerant is now cooled while being stirred until its pressure drops to 100 kPa. Determine the entropy change of the refrigerant during this process.

Previous question

Answer 1

The entropy change for refrigerant-134a cannot be accurately determined without additional details on the phase and specific entropy values at the initial and final states. Property tables or specialized software are needed for an exact calculation.

Step-by-step explanation:

The calculation of entropy change for refrigerant-134a or any other substance undergoing a thermodynamic process involves using the appropriate property tables or equations for entropy. In this problem, the refrigerant is cooled while being stirred, which implies that there could be a change of phase from vapour to liquid. The initial and final states need to be analyzed to find the entropy values at each state. However, since this problem description is incomplete and does not provide the necessary phase information or the specific entropy values at these states, a precise value for the entropy change cannot be calculated without additional information. Detailed property tables or software like REFPROP would typically be necessary to find the initial and final specific entropy values of refrigerant-134a.

Answer 2

To determine the entropy change of the refrigerant, we need to consider the initial and final states of the system. The change in entropy can be calculated using the formula ΔS = mcΔT / T. We need to know the specific heat capacity of refrigerant-134a at constant pressure to calculate the entropy change.

Step-by-step explanation:

To determine the entropy change of the refrigerant, we need to consider the initial and final states of the system. Initially, the refrigerant is at 20°C and 160 kPa and contains 5 kg of refrigerant-134a in a rigid tank. As the refrigerant is cooled while being stirred, its pressure drops to 100 kPa. The entropy change of the refrigerant can be calculated using the formula:

ΔS = mcΔT / T

Where ΔS is the entropy change, m is the mass of the refrigerant, c is the specific heat capacity of the refrigerant, ΔT is the change in temperature, and T is the temperature.

In this case, we need to know the specific heat capacity of refrigerant-134a at constant pressure to calculate the entropy change.