One kg of Refrigerant 22, initially at p1 = 0.9 MPa, u1 =

QUESTION:

One kg of Refrigerant 22, initially at \(p_{1}=0.9 \mathrm{MPa}, u_{1}=232.92 \mathrm{~kJ} / \mathrm{kg}\), is contained within a rigid closed tank. The tank is fitted with a paddle wheel that transfers energy to the refrigerant at a constant rate of 0.1 kW. Heat transfer from the refrigerant to its surroundings occurs at a rate Kt, in kW, where K is a constant, in kW per minute, and t is time, in minutes. After 20 minutes of stirring, the refrigerant is at \(p_{2}=1.2 \mathrm{MPa}, u_{2}=276.67 \mathrm{~kJ} / \mathrm{kg}\). No overall changes in kinetic or potential energy occur. (a) For the refrigerant, determine the work and heat transfer, each in kJ. (b) Determine the value of the constant K appearing in the given heat transfer relation, in kW/min.