1. The problem statement, all variables and given/known data One kg of Refrigerant 22 initially at p1=0.9 MPa, u1=232.92 kJ/kg, is contained within a rigid closd tank. The tank is fitted with a paddle wheel that transfers energy to the refrigerant at a constant rate of 0.1kW. 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 p2=1.2MPa. u2=276.7kJ/kg. Neglect kinetic and potential energy. Determine the value of the constant K appearing in the given heat transfer relation in kW/min. 2. Relevant equations 3. The attempt at a solution I've already found the work to be W= -120 kJ and the heat to be Q= -76.25 kJ What I'm struggling with is how to find the constant K. Bounds are from 0 to 20 minutes. Q=∫ Qdt =∫-Kt dt =-kt2/2 And now I'm stuck, I'm not sure what to do at this point. The next step shows K=(-2Q)/(t2) I have no idea how they got this.