PRE BOARD PIPE 7

50問 • 1年前

問題一覧

The gage pressure of a medium is 30 Kpa (vacuum) and the atmospheric pressure is 101.3 KPa, the absolute pressure will be;

71.3 Kpa

The Initial volume of an ideal gas is compressed to one-half its original volume and to twice its temperature the pressure,

Quadruples

An ammonia water cooled compressor receives the refrigerant at specific volume 62 L/kg. it has a piston displacement rate of 5 m^3/min. if a squirrel cage motor running at 1200 rpm drives the compressor and a average piston speed is 490 m/min, calculate size of cylinder bore.

16.13 cm

It is desired to double the COP of a reversed carnot engine for cooling from 5.0 by raising the temperature of heat addition while keeping the temperature of heat rejection constant. By what percentage must the temperature of heat addition he raised?

9.1 %

When a man returns to his well-sealed house on a summer day, he find that the house is at 32 degC . he turns on the air conditioner, which cools the entire house to 20 degC in 15 mins. If COP of the air-conditioner system is 2.5, determine the power drawn by the air conditioners. Assume the entire mass within the house equivalent to 800 kg of air for which c = 0.72 kj/kg-C.

3.07 KW

A two stage cascade vapor compression refrigeration system uses ammonia in the low-temperature loop and R-12 in the high-temperature loop. The ammonia provides 15 tons cooling. If the high-loop temperature requires 10.12 KW compressor power and low- loop 15.93 KW, determine the COP of the system.

2.027 TR

An ammonia refrigeration system the temperature in the evaporator is -12 degC the ammonia at the evaporator entry is 0.1511 dry while at exit is 0.95 dry, if the rate if ammonia circulation is 5.64 kh/min, determine the refrigerating capacity of the system. Enthalpy of saturated liquid and vapor at -12 degC us 144,929 kj/kg and 1447.74 kj/kg respectively.

27.82 TR

In an actual refrigeration cycle using R12 as working fluid, the refrigerant flow rate is 0.05 kg/s. vapor enters the expansion valve at 1.15 Mpa, 40 degC ( h=238.5 kj/kg) and leaves the evaporator at 175 KPa, -15 degC (h=345 kj/kg). the electric input to the motor driving the compressor is measured and found 3.0 KW. Motor efficiency at this load is 92% and mechanical efficiency 82%. Determine the actual coefficient of performance for this cycle.

2.36

Saturated vapor ammonia at -16 degC (h =1442.60 Kj/kg) leaves the evaporator and enters the compressor at -6 degC (h=1465 kj/kg). the refrigerant leaves the condenser as saturated liquid of 40 degC (h4 = 390.6 kj/kg) and enters the expansion valve at 35 degC (h3=366.1 kj/kg). heat rejects from the condenser amount to 50 KW. The work to compressor is 208 kj/kg, while the heat losses from compressor is 33 kj/kg. if 95 kj/kg of heat lost in the piping between the compress discharge and condenser inlet, determine the refrigerating capacity of the system.

13.24 TR

Three thousand cubic feet per minute of air are circulated over an air0cooled condenser. If the load of the condenser is 64,800 Btu/hr, compute the temperature rise of the air passing over the condenser specific volume of standard air (13.34 ft^3/lb)

20 degF

Reversed Carnot cycle has a refrigerating Cop of 2.5. determine the ratio TH/TL?

1.4

Twin cylinder ammonia compressor with volume displacement of 14,726 cm^3 operates at 300 rpm. Condenser and evaporator pressure re 1200 Kpa and 227 Kpa respectively. Specific volume of refrigerant at the entrance of compressor is 528.26 kj/kg. compression process is polytropic with n = 1.20 and clearance factor of compressor is 2 percent. Determine horsepower required.

80 HP

The refrigerant volume flow rate at the entrance of compressor were obtained from a test on a twin cylinder, single acting 15 cm x 20 cm, 320 rpm compressor ammonia refrigerating plant to be 33 L/s. determine the volumetric efficiency of the compressor.

87.6 %

Freon 22 air conditioning under standard operating conditions of 35 degC condensing and 5 degC evaporating temperatures, the volume flow rate entering the compressor is 23.72 L/s. determine the refrigerating capacity if the refrigerating effect is 164 Kj/Kg.

27.4 TR

An ammonia ice plant operates between a condenser temperature of 35 degC and evaporator of -15 degC. It produces 10 metric tons of ice per day from water at 30 degC to ice at -5 degC. Assuming simple saturation cycle, determine the horsepower of the motor if the adiabatic efficiency of the compressor is 0.85 and mechanical efficiency is 0.95. the specific heat of ice is 2.094 Kj/Kg-C and the latent heat is 335 Kj/kg.

21.9 HP

An ammonia simple saturation cycle operates with a suction pressure of 291.6 Kpa and a condenser pressure of 1204 Kpa develops 15 Tons of refrigeration. Determine the theoretical horsepower of the compressor.

13 HP

A house that was heated by electric resistance heaters consumed 1200 KWh electric energy in a winter month. If this house were heated instead by a heat pump that has an average performance factor PF of 2.4, determine how much money the homeowner would be saved that month assume a price of 0.0855 $/KWh for electricity.

$59.5

A refrigeration system is to cool bread loaves with an average mass of 450 g from 22 degC to -10 degC at a rate of 500 loaves per hour by refrigerated air. Taking the average specific and latent heats of the bread to be 2.93 Kj/kg – C and 109.3 KJ/Kg , respectively determine the product load.

761.5 KJ/min

An air conditioning system is used to maintain a house at 75 degF when the temperature outside is 95 degF. The house is gaining heat through the walls and windows at a rate of 1250 BTU/min, and the heat generation rate within the house from people, lights, and appliances amounts to 350 Btu/min. determine the minimum power input required for this air- conditioning system.

1.41 HP

A household refrigerator with EER 8.0 removes heat from the refrigerated space at a rate of 90 KJ/min. determine, the rate of heat transfer to the kitchen air

128.46 Kj/min

Carnot refrigerator operates in a room in which the temperature is 25 degC and consumes 2KW of power when operating. If the food compartment of the refrigerator is to be maintained at 3 degC, determine the rate of heat removal from the food compartment.

1504.8KJ/min

A Thermoelectric refrigerator that resembles a small ice chest is powered by a car battery, and has a COP of 0.10. If the refrigerator cools a 0.350 L canned drink from 20 degC to 4 degC in 30 mins, determine the average electric power consumed bu the thermoelectric refrigerator.

130 watts

A house s maintained at 22 degC in winter by electric resistance heater. If the outdoor temperature is 5 degC, the second law efficiency of the resistance heater is:

5.8 %

A water reservoir contains 100,000 kg of water at an average elevation of 60m. the maximum amount of electric power that can be generated from this water is:

16 KWh

Heat engine receives heat from a source at 1200 DegK at a rate of 500 Kj/s and rejects the waste heat to a sink 300 degK. If the power output of the engine is 200 KW, the second law efficiency of this heat engine is

53%

Air enters a turbojet engine at 200 m/s at a rate of 20 kg/s and exist at 800 m/s relative to the aircraft. The thrust developed by the engine is:

12 KN

Air in an ideal diesel cycle is compressed from 3 L to 0.15 L and then it expands during the constant pressure heat addition process to 0.3 L, under cold air standard conditions, the thermal efficiency of the cycle is

65 percent

A carnot cycle is operates between the temperature limits of 300 degK and 1500 degK and produces 500 KW of net power. The value of entropy change of the working fluid during the heat addition process is,

0.5 KW/k

An ideal gas mixture consist of 2 Kmol of N2 and 6 Kmol of CO2. The mass fraction of CO2 is:

0.825

Consider two Carnot heat engines operating in series. The first engine receives heat from the reservoir at 2400 degK and rejects the waste heat to another reservoir at temperature T. the second engine receives heat from the first one, convert sine if it to work, and rejects the rest to a reservoir at 300 degK. If thermal efficiencies of both engines are the same, determine the temperature T.

849 degK

An insulated box containing helium gas falls from a balloon 4.5 Km above the __________. Calculate the temperature rise in degC of the helium when the box hits the ground.

14.1

The rate of heat transfer to the surroundings from a person at rest is about 400 Kj/Hr. suppose that the ventilation system falls in an auditorium containing 120 people and assuming that the energy goes into the air of volume 1500 m^3 initially at 300 degK and 101 Kpa , calculate the rate in degC/min of air temperature change.

0.63

A simple Rankine produces 50 MW of power, 50 MW of process heated and rejects 50 MW of heat to the surroundings. What is the utilization factor of this cogeneration cycle neglecting the pump work?

64%

A 4 liter ( 2 liter per revolution at standard pressure temperature) spark engine has a compression ratio of 8 and 2200 KJ/kg Heat addition by the fluid combustion. Considering a cold air- standard Otto Cycle model, how much power will the engine produce when operating at 2500 rpm?

166.53 HP

A 12 DC electrical motor draws a current of 15 amps. How much work in KJ does this motor produce over a 10 minute period of operation?

108.0

Methyl alcohol (CH3OH) is burned with 25% excess air. How much unburned oxygen in kg-mol- oxygen/kg-mol-fuel will there be in the products if the product of combustion is compete?

0.37

A one cubic meter container contains a mixture of gases composed of 0.02 kg/mol of oxygen and 0.04 kg-mol helium at a pressure of 220 Kpa. What is the temperature of this ideal gas mixture in degrees kelvin?

441

An ideal gas with a molecular weight of 7.1 kg/kg is compressed from 600 Kpa and 280 degK to a final specific volume of 0.5 m^3/kg. during the process the pressure varies according to p= 620 + 150v + 95 v^2 where p is in KPa and V in m^3/kg. calculate the work of compression in KJ/kg?

33.33

An elastic sphere containing gas at 120 Kpa has a diameter of 1.0 m. heating the sphere causes it to expand its diameter of 1.3m, during the process the pressure is proportional to the sphere diameter. Calculate the work done by the gas in KJ.

87.5

A tank contains liquid nitrogen at -120 degC is suspended in a vacuum shell by three stainless steel rods 0.80 meter and 3 meters long with a thermal conductivity of 16.3 W/m^2-C. if the ambient air outside the vacuum shell is 15 degC. Calculate the magnitude of the conductive heat flow in watts along the supports rods.

0.168

A plate type solar energy collector with absorbing surface covered by a glass plate is to receive an inci... Radiation of 800 W/m^2. The glass plate has a reflectivity of 0.12 and a transitivity of 0.85. the absorbing surface has an absorptivity of 0.90. the area of the collector is 5 m^2. How much solar energy in watts is absorbed by the collector?

3060

An ocean-thermal energy conversion power plant generates 10,000 KW using a water surface water inlet temperature of 28 degC and a cold deep-water temperature of 15 degC, on the basis of a 3 DegC drop in the temperature of the warm water and a 3 DegC rise in the temperature of the cold water due to removal and addition of heat. Calculate the power required in KW to pump the cold0deeo water to the surface and through the system heat exchanger if the required pumping pressure increase is 20 KPa. Assume a carnot cycle efficiency and density of cold water to be 1000 kg/m^3.

250

A fan is powered by a 0.5 Hp motor and delivers air at a rate of 85 m^3/min. determine the highest value for the average velocity of air mobilized by the fan. Take the density of air to be 1.18 kg/m^3

21.12 m/s

In order to cool 1 ton (1000 kg) of water at 20 degC in an insulated tank, a person pours 80 kg of ice at -5 degC into the water. Determine the final equilibrium temperature in the tank. The melting temperature and the heat of fusion of ice at atmospheric pressure are 0 degC and 333.7 KJ/kg, respectively.

12.43 degC

A piston-cylinder device whose piston is resting on top of a set of stops initially contains 0.50 kg of helium of gas at 100 Kpa and 25 degC. The mass of the piston is such that 500 KPa of pressure is required to raise it. How much heat must be transferred to the helium before the piston starts rising?

1857.13 KJ

A student living in a 4m x 6m x 6m dormitory room turns on her 150 watts fan before she leaves the room on a summer day, hoping that the room will be cooled when she comes back in the evening, assuring all the doors and window are lightly closed and disregarding any heat transfer through the walls and the windows, determine a temperature in the room when she comes back 10 hours later. Use specific heat values at room temperature, and assume the room to be at 100 kpa and 15 degC in the morning when she leaves.

58.13 degC

4m X 5m x 6m room is to be heated by a baseboard resistance heater. It is desired that the resistance heater able to raise the air temperature in the room from 7 to 23 degC within 15 minutes. Assuming no heat losses from the room and an atmospheric pressure of 100 Kpa, determine the required power of the resistance heater. Assume constant specific heats at room temperature.

1.91 KW

A classroom that normally contain 40 people is to be air-conditioned with window air-conditioning units of 5 KW cooling capacity. A person at rest may be assumed to dissipate heat at a rate of about 360 Kj/hr. there are 10 light bulbs in the room, each with a rating of 100 watts. The rate of heat transfer to the classroom through the walls and the windows is estimated to be 15,000 Kj/hr. if the room air is to be maintained at a constant temperature of 21 degC, determine the number of window air-conditioning units required.

2 units

Water is being heated in a closed pan on top of a range while being stirred by a paddle wheel. During process, 30 kJ of heat is transferred to the water, and 5 KJ is lost to the surrounding air. The paddle wheel work amounts to 500 N- m. Determine the final energy of the system if its initial energy is 10 KJ

35.5 KJ

A supply of 50 kg of chicken at 6 degC contained in a box is to be frozen to -16 degC in a freezer. Determine the amount of heat that needs to be removed. The latent heat of the chicken is 247 kj/kg and its specific heat is 32 kj/kg-C above freezing and 1.77 Kj/kg- C below freezing. The container box is 5 kg and the specific heat of the box material is 1.4 kj/kg-C. also the freezing temperature of chicken is -2.8 C.

15,206.4KJ

machine design 2

ユーザ名非公開 · 5問 · 2年前

machine design 2