1.21 The thermal conductivity in a particular plane wall depends as follows on the wall temperature, T (°C): k = A + BT, where A and B are constants. The temperatures are T₁ and T2 on either side if the wall, and its thickness is L. By integration of Fourier's law, develop an expression for q. At what temperature should k be evaluated to avoid the need for integration?

Conduction Heat Transfer X material (a) material (b) . both (a) and (b) have the same thermal conductivity the temperature distribution is independent of thermal conductivity it's not that simple 9. Fin efficiency is defined as: • tanh (mL) (hP/k Ac)1/2 (heat transfer with fin) / (heat transfer without fin) (actual heat transfer through fin) / (heat transfer assuming all fin is at T = Tb) (Tx=L-Tf)/(Tb-Tf) 10. For an infinite fin, the temperature distribution is given by: (T-Tf)/(Tb-Tf)= e-mx. The heat flow through the fin is therefore given by: k (Tb-Tf)/L ● zero, because the fin is infinite ● infinite because the fin is infinite ● (Tb-Tf) (hP/k Ac)1/2 ● (Tb – Tf) (h P / k Ac)1/2 tanh (mL) 11. The Biot number, Bi, is defined as: • Bi=hk/L • Bi=hL/k • Bi= k/LH • Bi=qL/k • Bi=p UL/k 12. For a plate of length L, thickness, t, and width, W, subjected to convection on the two faces of area L x W. What is the correct length scale for use in the Biot number? . L ● W ● t • t/2 • L/2 13. If Bi…

*3.2 PQ1 A 100 mm diameter sphere contains an ideal gas at 20°C. Apply the grid method (p. 9) to calculate the density in units of kg/m³. a. Gas is helium. Gage pressure is 20 in H,O. b. Gas is methane. Vacuum pressure is 3 psi.

Q1. Honey is a very widely used ingredient in cooking all around the world. Many commercial honey manufacturers heat treat honey to remove harmful bacteria that may be present. The density and viscosity of the honey varies with temperature, as shown in table 1. Temperature K 293 298 303 308 313 318 323 Density kg/m³ 1403 1398 1393 1388 1383 1378 1373 Viscosity Pas 55.66 46.45 37.99 30.28 23.32 17.11 11.65 Table 1: Fluid properties of honey. A particular processing facility heats and sterilises 500 kg of unprocessed honey every 30 minutes. The unpro- cessed honey is stored in large vats, then pumped though pipes into heating units before being pumped through another pipe to be bottled. The pipe carrying the honey from a storage container, which is 11 m tall, to a heating unit is 5 m long and has a diameter of 10 cm. Prior to being heated the honey is kept at 25°C. (a) What is the pressure difference between the top and bottom of a storage vat when it is full? (b) What is the volume flow…