Effectiveness, ntu for heat exchangers. problem 4.9-4, p351. outlet temperature and effectiveness of an exchanger. hot oil at a flow rate of 3.00 kg/s (cp = 1.92 kj/kg×k) enters an existing counterflow exchanger at 400 k and is cooled by water entering at 325 k (under pressure) and flowing at a rate of 0.70 kg/s. the overall u = 350 w/m2 ×k and a = 12.9 m2. calculate the heat transfer rate and the exit oil temperature.

Coiled springs ought to be very strong and stiff. si3n4 is a strong, stiff material. would you select this material for a spring? explain.

Air inially occupying a volume of 1 m2 at 100 kpa, 27 c undergoes three internally reversible processes in series. process 1-2 compression to 500 kpa during which pv constant process 2-3 adiabatic expanslon to 100 kpa process 3-1: constant-pressure expansion to 100 kpa (a) calculate the change of entropy for each of the three processes. (b) calculate the heat and work involved in each process. (c) is this cycle a power cycle or refrigeration cycle?

Air enters a horizontal, constant-diameter heating duct operating at steady state at 290 k, 1 bar, with a volumetric flow rate of 0.25 m°/s, and exits at 325 k, 0.95 bar. the flow area is 0.04 m2. assuming the ideal gas model with k = 1.4 for the air, determine (a) the velocity at the inlet and exit, each in m/s, and (c) the rate of heat transfer, in kw flow rate, in kg/s, (b) the mass kg 0.3