For a boiling process such as shown in Figure 1.5 c, theambient temperature
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Fundamentals of Heat and Mass Transfer
- Q1) A steel cylinder 10 cm in diameter and 10 cm long is initially at 300 °C. It is suddenly immersed in an oil bath that is maintained at 40 °C, with h =280 W/m² °C. Find: (a) The temperature at the center of the solid after 2 min, and (b) The temperature at the center of one of the regular faces after 2 min.arrow_forward3.4 Estimate the rate of heat loss due to radiation from a covered pot of water at 95 ° C. How does this compare with the 60 W that is lost due only to convection and conduction losses? What amount of energy input would be needed to maintain the water at its boiling point for 30 minutes? The polished stainless steel pot is cylindrical, 20 cm in diameter and 14 cm high, with a tight-fitting flat cover. The air temperature in the kitchen is about 25 ° C. State any assumptions you make in deriving your estimatesarrow_forwardPLEASE SOLVE THE FOLLOWING THREE QUESTIONS Question G: Generally speaking, (no numbers required), at what point does Newton's Model of Cooling (T=A+Be^kx) (when regarding dead bodies' temperatures) no longer work? What in reality gives us an indication that we’ve taken it too far? Question H: Assuming that the temperature of the person at the time of death (TOD) was 98.6 °F, set up a TOD equation using the values of ,A, ,B, and k you’ve calculated. Then, solve the equation using the same logarithm method you used to solve for .k. A: 68 Farehneits, B: 17.9 Fareinheit K: -0.002564 TOD: 98.6 Fareinheit Plug the above info into Newton's law of cooling: (T=A+Be^kx) Write your answer as a time, not just as x minutes. Recall that when ,x=0, the time is 2:00 PM. Question I: When forensic expert determines the time of death, they often have additional information besides body temperature. Suppose a coroner finds that the person who was murdered had an infection that probably raised the…arrow_forward
- A piston cylinder assembly contains water. Heat is transferred to the cylinder in order to heat the water. The atmospheric pressure is equal to 100 kPa. Determine the boiling temperature of water if the mass of the piston is equal to 1000 g. Consider g= 10 m/s^2. The cross sectional area of the piston is equal to 100 cm^2. Select one: O a. 102.3 C O b. 97.92 C O c. 99.9 C O d. 103.4 Carrow_forward2. The initial temperature of the hot coffee cup is T(0) = 175°F. The cup is placed in a room temperature of T... = 70°F. The temperature T(t) of the coffee at time t can be approximated by Newton's law of cooling. ·+hT(t)=hT∞, where h is the convective heat transfer coefficient. dT dt (a) Find the transient solution, Ttran(t). (b) Find the steady-state solution. Tss(t). (c) Determine the total solution T(t). (d) Would increasing the value of h increase or decrease the time when the temperature of coffee reaches the room temp? (e) Would a lower or higher value of h be best for a cup of coffee?arrow_forwardIn thermodynamics, how do you differentiate a closed system with an adiabatic system? What is the difference in the equation used for calculating heat transfer? (If you know a good book or scientific article that contains info regarding this, please include. Thank you.)arrow_forward
- A solid hemisphere of radius 5 cm to be cooled in air (at 20 o C, h=10 W/m 2 .K) from 200 oC to center of 150 oC, assume following sphere properties ρ=8500kg/m3, k=20W/m.K , C=400 J/kg.Ka. List assumptions and justify selected method of solution b. How long does it take to cool the hemisphere? c. What is the temperature of the surface at end of cooling?arrow_forwardHow long should it take to boil an egg? Model the egg as a sphere with radius of 2.3 cm that has properties similar to water with a density of = 1000 kg/m3 and thermal conductivity of k = 0.606 Watts/(mC) and specific heat of c = 4182 J/(kg C). Suppose that an egg is fully cooked when the temperature at the center reaches 70 C. Initially the egg is taken out of the fridge at 4 C and placed in the boiling water at 100 C. Since the egg shell is very thin assume that it quickly reaches a temperature of 100 C. The protein in the egg effectively immobilizes the water so the heat conduction is purely conduction (no convection). Plot the temperature of the egg over time and use the data tooltip in MATLAB to make your conclusion on the time it takes to cook the egg in minutes.arrow_forwardAnswer this ASAP The diameter of the tube is 25 mm. The specific heat of water is 4.18 kJ/kg.°C. The overall heat transfer coefficient is 0.7 kW/m².°C. 1. Schematic of temperature distribution 2.ΔTLMTD 3.Actual heat transfer rate 4.Cmin 5.Maximum heat transfer ratearrow_forward
- Question 3 This question requires the use of the steam property tables (Rogers and Mayhew) uploaded on QM+ exam section. All properties should be evaluated at the temperature of the steam. Saturated, pure steam at a temperature of 170 °C condenses on the outer surface of a vertical tube of outer diameter 2 cm and length 1.5 m. The tube surface is maintained at a uniform temperature of 150 °C. Calculate: a) the local film condensation heat-transfer coefficient at the bottom of the tube. b) the average condensation heat-transfer coefficient over the entire length of the tube. c) the total condensation rate at the tube surface.arrow_forward= Consider a large plane wall of thickness L=0.3 m, thermal conductivity k = 2.5 W/m.K, and surface area A = 12 m². The left side of the wall at x=0 is subjected to a net heat flux of ɖo = 700 W/m² while the temperature at that surface is measured to be T₁ = 80°C. Assuming constant thermal conductivity and no heat generation in the wall, (a) express the differential equation and the boundary equations for steady one- dimensional heat conduction through the wall, (b) obtain a relation for the variation of the temperature in the wall by solving the differential equation, and (c) evaluate the temperature of the right surface of the wall at x=L. Ti до L Xarrow_forwardA composite plane wall consisting of materials, 1.5-in steel (k = 312 BTU-in/HR.ft2.0F) and 2-in aluminum (k = 1400 BTU-in/HR.ft2.0F), separates a hot gas at Ti = 2000F, hi = 2 BTU/HR.ft2.0F, from cold gas at To = 80 deg F, ho = 5. If the hot fluid is on the aluminum side, find: a) Transmittance, U; b) The heat through 100 sq. ft of the surface under steady state condition and c) The interface temperature at the junction of the metals.arrow_forward
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