A composite wall consisting of two layers of different materials in perfect thermal contactseparates the hot and cold fluids in a flat plate heat exchanger. Layer 1 is in contact withthe hot fluid at a temperature of 250 ºC for which the convective heat transfer coefficient is30 W/m2 K; layer 2 is in contact with the cold fluid at a temperature of 50 ºC for which theconvective heat transfer coefficient is 25 W/m2 K. Layer 1 has a thickness of 2 cm and athermal conductivity of 160 W/m K and layer 2 is 0.5 cm thick and has a thermalconductivity of 55 W/m K.a) (i) Sketch the schematic diagram describing the system(ii) What are the main heat transfer modes involved in the system above andwhere do they occur?(12 marks)b) Determine the overall heat transfer coefficient U.(10 marks)c) Calculate the heat flux q between the two fluids.(5 marks)d) Find the temperature at the interface between the two layers.
A composite wall consisting of two layers of different materials in perfect thermal contact
separates the hot and cold fluids in a flat plate heat exchanger. Layer 1 is in contact with
the hot fluid at a temperature of 250 ºC for which the convective heat transfer coefficient is
30 W/m2 K; layer 2 is in contact with the cold fluid at a temperature of 50 ºC for which the
convective heat transfer coefficient is 25 W/m2 K. Layer 1 has a thickness of 2 cm and a
thermal conductivity of 160 W/m K and layer 2 is 0.5 cm thick and has a thermal
conductivity of 55 W/m K.
a) (i) Sketch the schematic diagram describing the system
(ii) What are the main heat transfer modes involved in the system above and
where do they occur?
(12 marks)
b) Determine the overall heat transfer coefficient U.
(10 marks)
c) Calculate the heat flux q between the two fluids.
(5 marks)
d) Find the temperature at the interface between the two layers.
Step by step
Solved in 2 steps with 4 images
