A house is heated and maintained at 20 °C by a heat pump.Part APart BBased on these results, would you recommend heat pumps at locations with a severe climate?Match the words in the left column to the appropriate blankes in the sentences on the right.ResetHelpmild1. Given that a real heat pump is significantlyefficient than a Carnot heat pump, theincreasesadvantage of a heat pump over electric heatingrapidly when the outside temperaturebecomes really low.lessmore2. As the COP decreases, the heating powerdecreases3. A heat pump is ideal for aclimate.severeSubmitRequest Answer

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Principles of Heat Transfer (Activate Learning with these NEW titles from Engineering!)

8th Edition

ISBN:9781305387102

Author:Kreith, Frank; Manglik, Raj M.

Publisher:Kreith, Frank; Manglik, Raj M.

Chapter5: Analysis Of Convection Heat Transfer

Section: Chapter Questions

Problem 5.12P

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Question 2. A household with electric resistance heating plans to switch from resistive heating to a ground source heat pump. Annual heat consumption of the house is 30 000 kWh. Investment cost of the heat pump is 21 000 €. Heat pumps COP is 4.0. How much are the annual savings compared to resistive heating after the change of the heating system (in kWh)? Average price of electricity is assumed to be 12 c/kWh. Round off your answer to one decimal digit and enter it without the unit.
A steady-state electric motor operates under 10 Ampere and 220 Volt operating conditions. The output shaft rotates with 100 rpm (rpm) and 16 Nm torque. The heat transfer from the electric motor to the environment is related to the equation of surface temperature Tb, ambient temperature T0 and hA(Tb-T0). The energy transfer is shown on the figure with the help of arrows. (h=100 W/(m2K)), A= 0.195 m2, T0= 293 K) a) Determine the temperature Tb in K (Kelvin). b) Assuming the electric motor as the system, determine the entropy production in kW/K. c) Assume the area of the system boundary as the ambient temperature (T0) and determine the entropy generation in kW/K for the extended system boundaries.
In an experiment to measure the specific heat of material, a student first measured the masses of the following samples as given in Table 1. Table 1: Measurement of Mass Physical quantity measured in (g) Value Mass of Styrofoam 2.4 cup Mass of Styrofoam 62 cup + water Mass of Brass sample 15.3 Mass of Copper sample 62.5 and then recorded the temperatures of the above two samples, in Table 2. Table 2: Measured values of Temperatures Hot termperature ("C ) Sample Equilibrium cold temperature ( C) temperature ("C) Brass 99.8 26.5 24.5 Сopper 99.8 32 26 Answer the following questions using the data given in Table 1 and Table 2. (Please enter the answers with two digits after decimal) (a) Calculation of specific heat capacity of Brass: Calculated Quantities Mass of the water (in Values grams) Change in temperature lof the hot object ( ATobieca) °C) Change in temperature of water (ATwaer) (°C) Calculated specific heat of the object in (cal/g'C) (b) Calculation of the specific heat capacity…
01. A large plane wall, 7.5 cm thick, generates heat internally at the rate of 10 W/m³. One side of the wall is insulated, and the other side is exposed to an environment at 93°C. The convection heat transfer coefficient between the wall and the environment is 567 W/m K. If the thermal conductivity of the wall is 0.12 W/m-K. Assuming steady one-dimensional heat transfer, Determine: (a) The differential equation and the boundary conditions for the heat conduction through the wall, (b) obtain a relation for the variation of temperature in the wall by solving the differential equation, (c) determine the maximum temperature in the wall, in °C, and (d) calculate the heat flux through the wall.
V:01 Expert Q&A Done Question 1: In your own words, write down the differences between thermodynamic and heat transfer. (3 Marks) Question 2: Estimate the heat loss per square metre of surface through a brick wall 0.5 m thick when the inner surface is at 400 K and the outside surface is at 300 K. The thermal conductivity of the brick may be taken as 0.7 W/mK. (2 Marks) Question 3: A furnace is constructed with 0.20 m of firebrick, 0.10 m of insulating brick, and 0.20 m of building brick. The inside temperature is 1200 K and the outside temperature is 330 K. If the thermal conductivities are as shown in the figure below, estimate the heat loss per unit area. (5 Marks) 1200 K 330 K Insulating brick X-0.10m k= 0.21 Ordinary brick X=0.20 m Fire brick X= 0.20 m k= 1.4 k= 0.7 (W/mK)
Q1. A 50 meter long cast iron pipe with outer diameter of 10 cm passes in an open space of 288 K temperature. The outer surface of the pipe temperature is 423 K and the combined heat transfer coefficient on the outer surface of the pipe is 25 W/m? K. Considering and stating the necessary assumptions determine, (a) The rate of heat loss from the pipe (b) The energy lost per year if the cost of the fuel is 0.52 $/therm ( 1 therm = 105,500 kJ) (c) The thickness of the insulation if 98% of the energy loss is planned to be saved. Consider the conduction coefficient of the insulation is 0.035 W/mK. Tair = 288 K 423 K Steam 50 m Fiberglass insulation Figure Q1.
One of the greatest milestones in human civilization is the establishment of equivalence between heat and work by James Joule in 1840s. This set the stage for utilization of energy in fossil fuel to do work that leads to industrial revolution and the release of green-house gases. For sustainable growth with reduced damage to our environment and for the sake of future generation, the present generation need to do the followings: Use more renewable energy such as hydroelectricity, solar energy, wind energy, biodiesel, etc. (iii) Understand fluid dynamics better to design more efficient turbine, propeller etc. Re-organize our economy by introducing tax on the emission of carbon dioxide and carry out life-cycle analysis of energy utilization for products made. (A) (B) (i) and (ii) (i) and (iii) (ii) and (iii) All of the above
1. Steady state heat flow means, (a)Negligible flow of heat, (c)Heat flow independent of time (d)Uniform rate in temperature rise of a body 2. The ratio of heat flow QI/Q2 from two walls of same thickness having their thermal resistances as Rth1=8 Rth2 (b)No difference of temperature between the bodies will be: b) 0.25 3. The critical thickness of insulation for hot pipe is equal to: b) unity a) 0.125 c) 2 d) 4 a) h/k 4. Which of the following expresses thermal diffusivity of a substance in terms of thermal conductivity(k), density (p) and specific heat (C) a) (p2 k C) c) zero d) k/h d)(p C/k2) b) (1/ p k C) 5. The boundary condition of the end insulated fin are: c)(k/ p C) dT a) - kA() = 0 and T-To at x-0 b) - kA().- = 0 and T-Too at x=L dx d) None of them c) T=0 at x=0 and q=0 at x=L 6. The equation for the temperature profile inside a solid cylinder with heat source is: T-T a) T=T, + x b) =1-( !! 2k T,-T (R²-r) T-T = 2k c) d) None of them 7. Plane wall with heat generation, at x-0…
SANAE IV, a research station of The South African National Antarctic Programme (SANAP), is located on Vesleskarvet, Queen Maud Land. It uses an underground lake as the cold reservoir of a Carnot heat pump that maintains the temperature of a science lab at 307.8 K. To deposit 17360 J of heat in the lab, the heat pump requires 1086 J of work. Determine the temperature of water in the underground lake, in Kelvin.
(A) Choose the right answer 1.The temperature profile for heat conduction through a wall of constant thermal conductivity in the presence of heat source is a. straight line. b. parabolic. c. logarithmic. d. hyperbolic 2. A furnace wall has a thickness L=200 cm and k=0.1 W/(mK) with surface temperatures of 600°C and 400 C. The rate of heat transfer is a. 100 W/m? b. 200 W/m? c. 50 W/m? d. 300 W/m? 3. The ratio of heat transfer of a fin to the heat transfer without fin is referred to as a. fin effectiveness. b. b. fin efficiency. c. b. fin resistance. d. fin conductance. 4. The internal thermal resistance of a solid can be ignored if the Biot number is less than а. 0.1 b. 0.5 с. 1 d. Fourier number 5. The quantity having the dimension of time is often called the time constant of a thermocouple hA а. PCV hV b. c. PCV hA d. PCA hV PCA
nnoD :s D betae u 3. Temperature Rise in a Heating Wire. A current of 250 A is passing through stainless-steel wire having a diameter of 5.08 mm. The wire is 2.44 m long and has a resistance of 0.0843 N . The outer surface is held constant at 427.6 K. The thermal conductivity is k 22.5 W/m K. Calculate the center-line temperature at steady state. evard bae 0S 008 i 4R FO Ins
Please solve both parts with handwriting please need with correct answer need awesome answer solve both handwriting i requested to u. Part6. An exposed 8 cm external diameter, 20 m long hot-water pipe at 80°C is losing heat to the surrounding (outdoor) air by natural convection. The average outdoor temperature is 5°C. The heat transfer coefficient is 25 W/m2°C. What is the heat loss by natural convection, in kW? A. 9.4 W B. 10.0 W C. 10.4 W D. 11.4 W Part7. A spherical ball with a diameter of 10 cm has an outer surface that is maintained at a temperature of 200°C. It is suspended in the middle of a room that has an average temperature of 20°C. If the surface emissivity is 0.8, determine the rate of radiative heat transfer from the ball to the room in W. (Choose the nearest value) A. 2.3 W B. 4.5 W C. 19.4 W D. 60.8 W

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