Heat is transferred by radiation and convection between the inner surface of the nacelle of the wind turbine of Example 1.3 and the outer surfaces of the gearbox and generator. The convection heat flux associated with the gearbox and the generator may be described by
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Introduction to Heat Transfer
- A liquid reactant solution is pumped through a pre-heater before entering a reaction vessel. The solution enters the pre-heater at 25 °C and must enter the reactor at 45 °C. The flow of the reactant solution is 1500 mL per minute. The density of the reactant solution is 0.91 g-cm3 and the heat capacity is 1.75 Jg1.K1. ASsume there is no heat loss in the pre-heater or between the pre-heater and the reactor. a. Draw a schematic of the pre-heater, detailing all mass and energy flows. b. Clearly define a system boundary. c. Write the general energy balance, and a simplified energy balance stating all assumptions that apply to this problem. d. What is the minimum power rating required for the pre-heater?arrow_forwardQ1: Water at 80 oC is pumped through 100 m of stainless steel pipe, k=16 W/m.K of inner and outer radius 47 mm and 50 mm respectively. The heat transfer coefficient due to water is 2000 W/m2.K. The outer surface of the pipe loses heat by convection to air at 20 oC and the heat transfer coefficient is 200 W/m2.K. Calculate the heat flow through the pipe. Also calculate the heat flow through the pipe when a layer of insulation, k=0.1 W/m.K and 50 mm radial thickness is .wrapped around the pipearrow_forwardQi: (50 marks) Find the total heat flux of the composite wall when: B KA = KC = KF = 15 m. K KB = KD = 10 m. K KE = KG = 20 %3D m. K D. Height of B = C = D 4 cm 3 cm 4 cm 6 cm Height of F = G AT = 30 Karrow_forward
- Below is the dynamics of heat transfer: A container in an oven for instance dTc 1 1 ·TC+⋅ dt R+Ct -Tamb R+Ct In this equation, the container temperature Tc is the Output and the ambient temperature Tamb is the input. Thermal resistance and capacitance values are C+=7000 J/°C and R₁ = 0.0142858 W/°C. Initial condition is zero: Tc (0) = 0 °C. Obtain the transfer function of the system Create a table to compute its frequency response characteristics by considering low frequency region and high frequency region. Also consider a middle frequency. For low frequency region, consider a = 1e - 4 rad/s and w=1e-3-rad/s. For middle frequency, consider w=1e- 2 rad/s. For high frequency region, consider w = 1e-1 rad/s and w=1rad/s Using the magnitude and phase responses you tabulated, hand-sketch its Bode diagram. Clearly show low frequency and high frequency assumptions your drawing. Smoothen the diagram by considering the magnitude and phase at the middle frequency.arrow_forwardQ1. 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.arrow_forwardP2arrow_forward
- The time evolution of the temperature of an object follows the Newton's cooling laws dT dx = -k(T - Ts), where the term k = 2.2 (1/s) is the heat transfer constant, and Tg = 25.6° C is the ambient temperature. The initial temperature of the object at time t = = 0 is T(t = 0) = 200°C. °C Use the Euler's method, and a time step of h=0.2s, calculate: When t = = 0.2s, T = °C When t 1s, T =arrow_forwardSolve it correctly please. I will rate.arrow_forwardHello..arrow_forward
- Relationship to Thermodynamics 4. An electrical resistor is connected to a battery, as shown schematically. After a brief transient, the resistor assumes a nearly uniform, steady-state temperature of 95 °C, while the battery and lead wires remain at the ambient temperature of 25 °C. Neglect the electrical resistance of the lead wires Battery V=24 V Resistor dEst dt Air T. = 25C Lead wire (a) Consider the resistor as a system about which a control surface is placed and Equation 1.12c is applied. Determine the corresponding values of Ein(W), Eg(W), Eout (W), and Est(W). If a control surface is placed about the entire system, what are the values of in, Eg, Eout, and Est? (1.12c) Est Ein - Eout + Eg (b) If electrical energy is dissipated uniformly with in the resistor, which is a cylinder of diameter D= 60 mm and length L=250 mm, what is the volumetric heat generation rate, (W/m3)? (c) Neglecting radiation from the resistor, what is the convection coefficient?arrow_forwardA thermal system having a cylindrical form contains a sequence of cylindrical layers is used to cool hot gases. The thermal properties of the system materials are as follows : k = 231 W/m.K, c = 1033 J/kg.K and the density = 2702 kg/m^3. The gases to be cooled has a temperature equals to 500 C. Determine the temperature of the system that corresponds to 10 % of the maximum possible heat transfer between the gas and the system. Consider that the system has a characteristic length equals to 0.03 m. The heat convective coefficient is equal to 50 W/m^2.K. The initial temperature of the system is equal to 20 C. Select one: О а. 370 К O b. 489 K С. 341 К d. 410 Karrow_forwardPlease i need hand written solution on pages in 60 mins i will give you positive feedbackarrow_forward
- Principles of Heat Transfer (Activate Learning wi...Mechanical EngineeringISBN:9781305387102Author:Kreith, Frank; Manglik, Raj M.Publisher:Cengage Learning