A vapor absorption refrigeration system is a heat pump with three thermal reservoirs as shown in the figure. A refrigeration effect of $$100$$ $$W$$ is required at $$250$$ $$K$$ when the heat source available is at $$400$$ $$K.$$ Heat rejection occurs at $$300$$ $$K.$$ The minimum value of heat required (in $$W$$) is

In the velocity diagram shown below, $$u=$$ blade velocity, $$C=$$ absolute fluid velocity and $$W = $$ relative velocity of fluid and the subscripts $$1$$ and $$2$$ refer to inlet and outlet.