Water is to be heated from 12◦C to 70◦C as it flows through a 2 centimeter internal diameter, 7 meter long tube. The tube is equipped with an electric resistance heater, which provides uniform heating throughout the surface of the tube. The outer surface of the heater is well insulated, so that in steady operation all of the heat generated in the heater is transferred to the water in the tube. If the system is to provide hot water at a rate of 8 L/min, determine the power rating of the resistence heater. Also, estimate the inner surface temperature of the pipe at the exit.

Consider a steam power plant that operates on a reheat Rankine cycle and has a net power output of 80 MW.
Steam enters the high-pressure turbine at 10 MPa and 500°C and the low-pressure turbine at 1 MPa and 500°C. Steam leaves the condenser as a saturated liquid at a pressure of 10 kPa. The isentropic efficiency of the turbine is 80 percent, and that of the pump is 95 percent. Show the cycle on a T-s diagram with respect to saturation lines, and determine (a) the quality (or temperature, if superheated) of the steam at
the turbine exit, (b) the thermal efficiency of the cycle, and (c) the mass flow rate of the steam.k

A new refrigerator is being designed. Magnets will be used to hold the door closed, and the rubber seal thickness can be selected to adjust the separation between the magnets (and therefore the force). The total length of rubber seal required to go around the door is 6m, and the cost of rubber seal is given equation 2. The pull force when opening the door should be 12N. Determine which of the magnet combinations should be used, and the combined cost of the magnets and seals per refrigerator.

Table 2. Material costs of neodymium magnets

$Cost/m of rubber seal = 30 T^-0.7                    Equation 2

where T = thickness of each seal in mm (half the separation between the magnets)

A ship is fitted with six-cylinder CI engine of 75 mm bore and 100 mm stroke. The engine has a brake power output of 110 kW at 370 rpm. The volumetric efficiency at this operating condition, referred to ambient conditions, of 1.013 bar and 20˚C is 80%. You have just fitted a mechanically driven supercharger which has isentropic efficiency of 0.7 and the pressure ration of 1.6. The supercharged version of the engine has a volumetric efficiency of 100% referred to supercharged delivery pressure and temperature. It is assumed that the indicated power developed, per unit volume flow rate of induced air at ambient, is the same for normal and supercharged engine. Determine the net increase in brake power to be expected from the supercharged engine. Take the mechanical efficiency of the engine to be 80% in both cases and mechanical efficiency of the drive from the engine to supercharger as 95%.

Heat Transfer Problem

You had been assigned, at General Motors as a design engineer, to design a radiator (Heat Exchanger) for a new model car . It is necessary that the heat exchanger will be compact enough to fit within a space of 2 feet by 3 feet available in front of the car. IF the temperature of the incoming engine coolant is 150 degree Centigrade and the outside temperature of air is about 38 C:

What type of heat exchanger could reduce the temperature of the coolant to 40 C? find the surface area and number of the tubes necessary to do so. Select the Coolant properties as water. The coolant is circulated by a water pump at a rate of 0.5 kg/sec. Show all your work and justify the selection you made. Make all other engineering assumptions necessary for this design.

heat transfer question, show equations, assumptions, calculations and steps clearly. will give thumbs up rating if solved correctly in 30 minutes

part a:

One of your hands is in still air at room temperature while the other one is in still water also at room temperature. Which hand will feel colder and why?

part b:

Why does sunscreen lotion prevent you from getting sunburn, but not from feeling the heat from the sun?

Please explain the meaning of design and analysis on automotive term. thanks

Consider a steam power plant operating on the ideal reheat Rankine cycle. Steam enters the high-pressure turbine at P_H MPa and T_H °C and is condensed in the condenser at a pressure of P_L kPa. Assume the steam is reheated to the inlet temperature of the high-pressure turbine, and that pump work is NOT negligible. If the moisture content of the steam at the exit of the low-pressure turbine is not to exceed w_% percent, determine:

(a) the pressure at which the steam should be reheated ,

(b) the total turbine work ,

(c) the net work ,

(d) the total heat input , and

(e) the thermal efficiency of the cycle .

P_H = 17.5 MPa, T_H = 600 °C, P_L = 15 kPa and w_% = 9.9%.

A sleeve coupling is used to connect two 50 mm shafts whose safe shearing stress is 70 MPa. Design the sleeve when it is made of cast iron with an ultimate shearing stress of 140 MPa. Also determine the factor of safety for which the sleeve has been designed. The length of the key is half the length of sleeve and the section of the key is 12.5 mm x 12.5 mm, find the shearing and crushing stresses induced in the key used.

A mechanical aim rotates in the vertical plan about point O. The slider P (m = 2 kg) is drawn toward O with a constant speed (?̇) of 0.5 m/s through the rough slot (friction coefficient µ = 0.1) by pulling on the free end E of the cord. At the instant when r = 0.25 m, the arm is rotating with a constant speed (?̇) of 10 rad/s in the clockwise direction.


When the slider is oriented at an angle of θ = 30° from the horizontal:

a) Plot the free body diagram for P, using r-? coordiantes; show positive r and ? directions (4 points)

b) Determine the normal force between the slider and the slot, in N (7 points)

c) Determine the tension in the cord, in N (7 points)

d) Which side (A or B) is in contact with the slider? Why? (2 points)

The air inside inside a house is 14 ^oC and the convective heat transfer coefficient h = 11 W/m2⋅°C. The air outside the house is 49 ^oC and the convective heat transfer coefficient h = 7 W/m2⋅°C. A window has dimensions (2m x 2.5m x 8mm) and heat conduction of 0.8W/mk. Determine the total heat resistance through the window in ^oC/W