Three electric resistance heaters of length
(a) If the heaters are activated, each dissipating
(b) If the natural convection coefficient ¡s given by an expression of the form
(c) If the heaters are inadvertently activated when the tank is empty, the natural convection coefficient associated with heat transfer to the ambient air at
also 300 K and the emissivity of the heater surface is
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Fundamentals of Heat and Mass Transfer
- Answer with a clean and neat solution In a piston cylinder system, the gas an initial pressure of 100 kPa and expands from 1.5 m3 to 7.5 m3 with an increase in internal energy amounting to [50 + (162/20)] kJ. Calculate the heat gain or loss in the system given the pressure volume relation as P2V is constant, where P is in kPa and V is in m3.arrow_forwardLiquid A has a density of 0.85 kg/m3 and a specific sensible heatcapacitance (Cv) of 2.2 kJ/kgK. Liquid B has a density of 0.78 kg/m3and a specific sensible heat capacitance (Cv) of 1.8 kJ/kgK. Liquid A isat 22°C and liquid B is at 14°C. Equal volumes of both liquids are mixedtogether. What is the resulting temperature? answer is 18.6°Carrow_forwardB-Water flows at Too 50 °C, hoo1 = 3500 W/m² ° C in a pipe with r₁= 1.25 cm, r₂ =1.33 cm and L= 1 m, the pipe has k= 16 W/m °C. The outside of the pipe is exposed to a fluid with Too2 = 20° C, hoo₂ 7.6 W/m² ° C. Calculate the rate of heat lost by the pipe and find the temperature of the pipe outer surface T₂. 0 3 + 6 f = =arrow_forward
- Determine the quantity (volume) of saline water in a steam generator. The heat energy of 1576 kJ is supplied to saline water in the steam generator to heat from 22°C to 123°C for the generation of water vapor, Take the density & specific heat of the solution as 1033 kg/m & 3.7 J/kg°K respectively. Solution: Change in Temperature (in K) 101 Mass of the saltwater (in kg) 4217.28 Quantity (Volume) of saltwater (in m) 4.082arrow_forward(heat transfer ) thanks The velocity of the fluid flowing in parallel over a 500mmx500mm flat heater surface is U= 19 m/s and the inlet velocity temperature is T_∞15 C. The surface temperature of this plate is T_s140 C, the friction force is F_D=0.4 N and the surface area of the plate is A=0.32 m2. According to this;(F_D= 0.4N A=32 m2)a) Surface shear stressb) Find the coefficient of frictionc) Heat transfer coefficientd) What is the amount of heat transfer (electric power) that must be given to maintain a constant surface temperature?arrow_forwardA cylinder of cross-section area A is divided into two chambers 1 and 2, by means of a frictionless piston. The chambers initially have equal length L. Both chambers are filled with 1 mole of ideal gas, wlth initial pressures M 2Po and Po, respectively. The piston is then allowed to slide freely, whereupon the gas in chamber 1 pushes the piston a distance 1 to equalize the pressure. Consider the following two cases: m (i) The outer walls of the chambers and the piston do not w w mw m allow heat transfer. Denote the distance l as la in this case. (ii) The piston does not allow heat transfer but the chambers are in contact with two heat reservoirs w ww separately, at temperature Tl and T2 for chambers 1 and 2, respectively. Denote the distance 1 as ld in this case. Calculate the ratio la/ld ? Does this ratio have a small or big valaarrow_forward
- Determine the quantity (volume) of saline water in a steam generator. The heat energy of 1624 kJ is supplied to saline water in the steam generator to heat from 24°C to 101°C for the generation of water vapor, Take the density & specific heat of the solution as 1015 kg/m³ & 4.6 J/kg°K respectively. Solution: Change in Temperature (in K) Mass of the saltwater (in kg) Quantity (Volume) of saltwater (in m3)arrow_forwardyou are asked to design a heating system for a swimming pool that is 2m deep 25 m long and 25 m wide. your client desires that the heating system to be large enough to raise the water temperature from 20 to 30° C in 3h.the rate of heat loss from the water to the air at the outdoor design conditions is determined to be 960W/m^2 and the heater must also be able to maintain the pool at 30° C at those conditions.heat loses to the ground are expected to be small and can be disregarded.the heater considered is a natural gas furnace whose efficiency is 80 percent. what heater size (in kW input) would you recommend to your client?arrow_forwardDetermine the quantity (volume) of saline water in a steam generator. The heat energy of 1525 kJ is supplied to saline water in the steam generator to heat from 25°C to 114°C for the generation of water vapor, Take the density & specific heat of the solution as 1031 kg/m' & 4.5 J/kg°K respectively. Solution: Change in Temperature (in K) Mass of the saltwater (in kg) Quantity (Volume) of saltwater (in m2) earch 立arrow_forward
- determine the value of AB. Water is to be heated from 20°C to 70°C as it flows through a 40 mm internal diameter and 600 mm long tube. The outer surface of the tube is wrapped with electrical wire which acts as an electrical resistance heater. The heater provides uniform heat flux throughout the surface of the tube. The outer surface of the heater is well insulated. At steady state if the system provides hot water at 0.2475 kg/s, determine the power rating of the resistance heater and the inner surface temperature of the pipe at the exit. Р = 990 kg/m³; k = 0.631 W/(m K); c Pr-4.328 = 4180 J/(kg K); v = 0.66 x 10-6 m²/s:arrow_forwardConduction 1. A thermodynamic analysis of a proposed Brayton cycle gas turbine yields P= 5 MW of net power production. The compressor, at an average temperature of T. = 400°C, is driven by the turbine at an average temperature of T₁ = 1000°C by way of an L = 1m-long, d= 70mm - diameter shaft of thermal conductivity k = 40 W/m K. Compressor min T Combustion chamber Shaft L Turbine Th out (a) Compare the steady-state conduction rate through the shaft connecting the hot turbine to the warm compressor to the net power predicted by the thermodynamics- based analysis. (b) A research team proposes to scale down the gas turbine of part (a), keeping all dimensions in the same proportions. The team assumes that the same hot and cold temperatures exist as in part (a) and that the net power output of the gas turbine is proportional to the overall volume of the device. Plot the ratio of the conduction through the shaft to the net power output of the turbine over the range 0.005 m s Ls 1 m. Is a…arrow_forwardSolve for the latent heat of water at Tw = 28C(and. λw = 2435 kJ/kg)arrow_forward
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