The 150-mm-thick wall of a gas-fired furnace is constructed of fireclay brick
(a) How long does it take for the outer surface of the wall to reach a temperature of 750°C’?
(b) Plot the temperature distribution in the va1l at the foregoing lime, as well as at several intermediate times.
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Introduction to Heat Transfer
- 1. A four -cylinder Carnot engine having a 90 x 120-mm bore and stroke operates between 420 deg C and 30 deg C . The engine rejects 20 KJ of heat to the atmosphere while running at 320 rpm . Determine the mean effective pressure in KPa 2.One kg of gas at 240 OC,expands adiabatically , so that its volume is doubled and the temperature falls to 115 OC . The work done during expansion is 90 KJ.Determine the molecular weight of this gas .arrow_forwardDetermine if the statement is TRUE or FALSE On cooling below the critical temperature, entropy of superconducting materials decreases considerably.arrow_forwardStainless-steel ball bearings (ρ = 8085 kg/m3 and cp = 0.480 kJ/kg·°C) having a diameter of 1.8 cm are to be quenched in water at a rate of 1100 per minute. The balls leave the oven at a uniform temperature of 900°C and are exposed to air at 20°C for a while before they are dropped into the water. If the temperature of the balls drops to 850°C prior to quenching, determine the rate of heat transfer from the balls to the air.arrow_forward
- The roofs of many homes in the United States are covered with photovoltaic (PV) solar cells that resemble roof tiles, generating electricity quietly from solar energy. An article stated that over its projected 30-year service life, a 4-kW roof PV system in California will reduce the production of CO2 that causes global warming by 433,000 lbm, sulfates that cause acid rain by 2900 lbm, and nitrates that cause smog by 1660 lbm. The article also claims that a PV roof will save 253,000 lbm of coal, 21,000 gallons of oil, and 27 million ft3 of natural gas. Making reasonable assumptions for incident solar radiation, efficiency, and emissions, evaluate these claims and make corrections if necessary.arrow_forwardA mass of 300kg of oil is cooled in 1 hour from 70 celcius to 35 celcius in a cooler consisting of a bank of tubes through which hot oil passes. Cooling water circulates around the outside of the tubes. Calculate the mass of cooling water required per hour if the water temp increases by 21 degrees celcius . Specific Heat of Oil - 2.0 kJ/kg deg C Specific Heat of Water - 4.186 kJ/kg deg Carrow_forwardA monatomic ideal gas initially fills a V0 = 0.35 m3 container at P0 = 75 kPa. The gas undergoes an isobaric expansion to V1 = 0.85 m3. Next it undergoes an isovolumetric cooling to its initial temperature T0. Finally it undergoes an isothermal compression to its initial pressure and volume. Part (h) Calculate the work done by the gas, W3, in kilojoules, during the isothermal compression (third process). Part (i) Calculate the change in internal energy, ΔU3, in kilojoules, during the isothermal compression (third process). Part (j) Calculate the heat absorbed Q3, in kilojoules, during the isothermal compressions (third process).arrow_forward
- In the context of a Spark Ignition (SI) engine, consider a moment during combustion when there is a heat flux through the wall of the combustion chamber at a specific location, measured at 219 kW/m2. The gas temperature within the cylinder at this time is 2300 K, and the convection heat transfer coefficient within the cylinder is 120 W/m2⋅K. The coolant temperature is 80 °C. The thickness of the cylinder wall is 10mm with a thermal conductivity of 200 W/m⋅K. (a) Determine the temperature of the inner surface of the cylinder wall. (b) Find the temperature on the side of the cylinder wall facing the coolant. (c) Calculate the heat transfer coefficient on the coolant side of the cylinder wallarrow_forward3. A lumped system with a volume of 0.003 m³ and a surface area of 0.08 m² is made of a material with density of 3800 kg/m³, thermal conductivity of 300 W/m K, and specific heat of 200 J/kg K. If the system is exposed to a convection environment with h = 60 W/m2 K, what is the approximate time it will take for this system to reach equilibrium with the environment? Express your answer in minutes.arrow_forward) Stainless steel ball bearings (ρ = 8085 kg/m3and cp = 0.480 kJ/kgC) having adiameter of 1.22 cm are to be quenched in water at a rate of 1402 per minute.The balls leave the oven at a uniform temperature of 900C and are exposed to air at 300C for a while before they are dropped into the water. If thetemperature of the balls drops to 855C prior to quenching, determine:(i) The rate of heat transfer from the balls to the air; and(ii) The rate of entropy generation due to heat loss from the balls to the air.arrow_forward
- Calculate the total heat gain of a restaurant at its peak occupancy load at about 1PM. When hundred dinners and 15 employees are present, Given: Heat gain through wall and roof: 2500Kj/hr; Heat gain through glass areas:500Kj; Number of florescent tube lights:60; Rating of each tube light:40W; Rating of toasters inside space:2650W; Sensible heat gain per dinner:250Kj/hr; Latent heat gain per dinner: 260Kj/hr Sensible heat per employee:305Kj/hr Latent heat per employee:545Kj/hr Inside design conditions:25 oC DB, 19 oC WB Outside design conditions: 40 oC DB, 27 oCWB Ventilation requirement: 0.4cmm/personarrow_forwardQuestion 2a) Give the Stefan Boltzman equation and define each term.[4]b) A electric room heater (radiator) element is 25 cm long and 4 cm in diameter. The element dissipates heat to the surroundings at 1500 W mainly by radiation, the surrounding temperature being 15°C. Determine the equilibrium temperature of the element surface.[4]c) A composite cylinder consists of 10 cm radius steel pipe of 25 mm thickness over which two layers of insulation 30 mm and 35 mm are laid. The conductivities are 25 W/mK, 0.25 W/mK and 0.65 W/mK. The inside is exposed to convection at 300°C with h 65 W/m2K.The outside is exposed to air at 30°C with h 15 W/m2K. Determinei. the heat loss/m,the interface temperatures.ii. The overall heat transfer coefficient.[4][4][2]arrow_forwardThe following heat engines produce power 95,000 kW. Determine in each case the rates at which heat is absorbed form the hot reservoir and discarded to the cold reservoir. a. A Carnot engine operates between heat reservoirs 750K and 300K b. A practical engine operates between the same heat reservoir but with a thermal efficiency η = 0.35arrow_forward
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