Total R-Value The R-values of any two or three materials can be added to determine the total R-value (R.).
11) Find the total R-value for the walls below.
a) Calculate R, for Wall A.
b) Calculate R for Wall B.
c) Which do you prefer and why?
Wall A
Wall B
Outside: Concrete Block (4") Outside: Brick (4")
Middle: Cellulose in Wall (1") Middle: 1" air space
Inside: Plywood (5/8")
Inside: Plywood (5/8")

Athin walled concentric tube exchanger is used to cool engine oil from 160°c to 60°c with water that is available at 25°c acting as a coolant. the oil and water flow rates are each at 2 kg/s, and the diameter of the inner tube is 0.5 m and the corresponding value of the overall heat transfer coefficient is 250 w/m2. oc. how long must the heat exchanger be to accomplish the desired cooling? cpwater=4.187 kj/kg-candcpengine el=2.035 kj/kg·°c, oil . 120]