A gas refrigeration cycle with a pressure ratio of 4 uses helium as the working fluid. The temperature of the helium is -6°C at the compressor inlet and 50°C at the turbine inlet. Assume isentropic efficiencies of 88 percent for both the turbine and the compressor.

(Given: The properties of helium are c_p= 5.1926 kJ/kg·K and k = 1.667.)

FIND:

a. The minimum temperature of the cycle.

b. The coefficient of performance.

c. the mass flow rate of the helium.

The atmospheric air 32 °C dry bulb temperature and 70% relative humidity supplied to the cooling coil at a rate of 45m3 /min. The air cooling to the saturated state and leaving at a temperature of 16 °C. Determine: () a- Specific humidity at each state. b- Wet bulb and dew point temperatures at the final state c- Final relative humidity. d- Mass of water condensed. e- Rate of heat removed from the air in kW. f- Show the process on Psychrometric chart

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how to calculate a shaft diameter of horizontal wind turbine

Indicate whether the following statements are true or false. Explain.

1. Rate of energy transfer induced as a result of a temperature difference between a system and its surroundings is called a power.
2. When a system undergoes a process, the terms work and heat are refer to what is being transferred.
3. If an object of known mass and initially at rest falls from a specified elevation, then hits the ground and comes to rest at zero elevation. It means its kinetic energy is converted to potential energy.
4. The three modes of energy storage for individual atoms and molecules making up the matter within a system are kinetic, potential, and internal energies.
5. For any cycle, the net amounts of energy transfer by heat and work are equal.
6. Current passes through an electrical resistor inside a tank of gas. The energy transfer can be considered work.
7. The internal energy of a system at a state has significance.
8. In the case of refrigeration, its coefficient of performance is always greater or less than one.
9. Is it correct to say that a system contains heat?
10. Adiabatic process involving no heat transfer by energy.

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A turbo fan blades of an airplane is made from hard material which is titanium.

a) Suggest the most suitable non-traditional machining process that can be used to produce the turbo fan blades

b) Referring to your answer in (a), briefly describe the machining principle. A sketch may help to facilitate your explanation.

c) List three advantages and two disadvantages of the process.

You are using a silver spoon to stir water that just started boiling so that you can achieve a more even heat distribution in your water. The spoon is partially immersed in boiling water and a thermometer in your kitchen reads 27 °C. The handle of the spoon has a cross section of 2mm × 1cm and extends 15 cm in the air from the free surface of the water. The heat transfer coefficient at the exposed surfaces of the spoon handle is 3 W/m2 ×K. Part A : Determine the temperature difference across the exposed surface of the spoon handle. Follow the problem-solving guide on the front page. At the minimum, your analysis should answer the following questions providing detailed justifications:

1. What are the modes of heat transfer that the spoon is exposed to?

2. Is this a time dependent or steady state problem? Why or why not?

3. Is this a 1-D, 2-D or 3-D problem? Why or why not?

4. What is the thermal conductivity of the material? Can you assume it constant and if so, for what ranges?

5. The heat transfer coefficient is a function of many variables. Discuss the variables and whether the heat transfer coefficient can be assumed to be constant.

Write down the reasons why motors draw overcurrent from the mains and the names and protection types of motor protection relays used against this risk.
COMMAND AND POWER CIRCUIT IS A WHOLE IN QUESTIONS
The control circuit of the three asynchronous motors by answering the following requests
A) The second engine will not operate while the first or third engine is running
B) While the first or second engine is running, the third engine will not work.
C) When the first motor is stopped due to over current or by pressing the stop button, all
engines will stop.
D) Each engine can be operated separately.

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%.