Apizza of diameter d is resting on top of a granite counter top to which it loses heat via conduction. the pizza also loses heat to the surrounding air via convection. derive an expression for the total thermal resistance seen by the pizza. both the countertop and the air are at the same temperature, t.

Apiping systems consists of 6 m of 6-std type k and 12 m of 4-std type k, both drawn copper tubing. the system conveys ethylene glycol at a rate of 0.013 m3/s. the pressure drop across the system is to be calculated. there are two 90° elbows in the 6-in pipe, a reduction from the 6-in pipe to the 4-in pipe and four 90° elbows in the 4-in pipe. all fittings are soldered (same as flanged) and regular. the inlet and outlet of the system are at the same height.