Questions and Answers of Fundamentals Thermal Fluid

Repeat Prob. 18–108 using a banana instead of an apple. The thermal properties of bananas are practically the same as those of apples.Repeat Prob.Conduct the following experiment at home to
A company owns a refrigeration system whose refrigeration capacity is 200 tons (1 ton of refrigeration = 211 kJ/min), and you are to design a forced-air cooling system for fruits whose diameters do
Design a hydrocooling unit that can cool fruits and vegetables from 30°C to 5°C at a rate of 20,000 kg/h under the following conditions:The unit will be of flood type that will cool the products as
Water flows through a shower head steadily at a rate of 8 kg/min. The water is heated in an electric water heater from 15°C to 45°C. In an attempt to conserve energy, it is proposed to pass the
Thermal comfort in a house is strongly affected by the so-called radiation effect, which is due to radiation heat transfer between the person and surrounding surface. A person feels much colder in
Radiation shields are commonly used in the design of superinsulations for use in space and cryogenics applications. Write an essay on superinsulations and how they are used in different applications.
According to an Atomic Energy Commission report, a hydrogen bomb can be approximated as a large fireball at a temperature of 7200 K. You are to assess the impact if such a bomb exploded 5 km above a
Write an essay on the radiation properties of selective surfaces used on the absorber plates of solar collectors. Find out about the various kinds of such surfaces, and discuss the performance and
The top surfaces of practically all flat-plate solar collectors are covered with glass in order to reduce the heat losses from the absorber plate underneath. Although the glass cover reflects or
Contact a manufacturer of aluminum heat sinks and obtain their product catalog for cooling electronic components by natural convection and radiation. Write an essay on how to select a suitable heat
A desktop computer is to be cooled by a fan. The electronic components of the computer consume 80 W of power under full-load conditions. The computer is to operate in environments at temperatures up
Design a heat exchanger to pasteurize milk by steam in a dairy plant. Milk is to flow through a bank of 1.2-cminternal-diameter tubes while steam condenses outside the tubes at 1 atm. Milk is to
Electronic boxes such as computers are commonly cooled by a fan. Write an essay on forced air cooling of electronic boxes and on the selection of the fan for electronic devices.
Conduct this experiment to determine the heat loss coefficient of your house or apartment in W/°C or Btu/h.°F. First make sure that the conditions in the house are steady and the house is at the
Conduct the following experiment to determine the time constant for a can of soda and then predict the temperature of the soda at different times. Leave the soda in the refrigerator overnight.
Conduct the following experiment at home to determine the combined convection and radiation heat transfer coefficient at the surface of an apple exposed to the room air. You will need two
Using a timer (or watch) and a thermometer, conduct this experiment to determine the rate of heat gain of your refrigerator. First, make sure that the door of the refrigerator is not opened for at
A house with 200-m2 floor space is to be heated with geothermal water flowing through pipes laid in the ground under the floor. The walls of the house are 4 m high, and there are 10 single-paned
Using cylindrical samples of the same material, devise an experiment to determine the thermal contact resistance. Cylindrical samples are available at any length, and the thermal conductivity of the
In the design of electronic components, it is very desirable to attach the electronic circuitry to a substrate material that is a very good thermal conductor but also a very effective electrical
The temperature in deep space is close to absolute zero, which presents thermal challenges for the astronauts who do space walks. Propose a design for the clothing of the astronauts that will be most
It is well-known that at the same outdoor air temperature a person is cooled at a faster rate under windy conditions than under calm conditions due to the higher convection heat transfer coefficients
Conduct this experiment to determine the combined heat transfer coefficient between an incandescent lightbulb and the surrounding air and surfaces using a 60-W lightbulb. You will need a thermometer,
Using information from the utility bills for the coldest month last year, estimate the average rate of heat loss from your house for that month. In your analysis, consider the contribution of the
Write an essay on how microwave ovens work, and explain how they cook much faster than conventional ovens. Discuss whether conventional electric or microwave ovens consume more electricity for the
Many drivers turn off their air conditioners and roll down the car windows in hopes of saving fuel. But it is claimed that this apparent “free cooling” actually increases the fuel consumption of
Large commercial airplanes cruise at high altitudes (up to about 40,000 ft) to save fuel. Discuss how flying at high altitudes reduces drag and saves fuel. Also discuss why small planes fly at
Write a report on the flaps used at the leading and trailing edges of the wings of large commercial aircraft. Discuss how the flaps affect the drag and lift coefficients during takeoff and landing.
During a camping trip you notice that water is discharged from a high reservoir to a stream in the valley through a 30-cm-diameter plastic pipe. The elevation difference between the free surface of
A pump is to be selected for a waterfall in a garden. The water collects in a pond at the bottom, and the elevation difference between the free surface of the pond and the location where the water is
Visit a fire station and obtain information about flow rates through hoses and discharge diameters. Using this information, calculate the impulse force to which the firefighters are subjected when
Using a flexible drinking straw and a ruler, explain how you would measure the water flow velocity in a river.
Using a handheld bicycle pump to generate an air jet, a soda can as the water reservoir, and a straw as the tube, design and build an atomizer. Study the effects of various parameters such as the
Computer-aided designs, the use of better materials, and better manufacturing techniques have resulted in a tremendous increase in the efficiency of pumps, turbines, and electric motors. Contact one
Shoes are to be designed to enable people of up to 80 kg to walk on freshwater or seawater. The shoes are to be made of blown plastic in the shape of a sphere, a (American) football, or a loaf of
Write an essay on the oils used in car engines in different seasons and their viscosities.
Write an essay on the rise of the fluid to the top of trees by capillary and other effects.
Design an experiment to measure the viscosity of liquids using a vertical funnel with a cylindrical reservoir of height h and a narrow flow section of diameter D and length L. Making appropriate
A refrigerator using R-12 as the working fluid keeps the refrigerated space at 215°C in an environment at 30°C. You are asked to redesign this refrigerator by replacing R-12 with the ozone-friendly
Write an essay on air-, water-, and soil-based heat pumps. Discuss the advantages and the disadvantages of each system. For each system identify the conditions under which that system is preferable
Contact your power company and obtain information on the thermodynamic aspects of their most recently built power plant. If it is a conventional power plant, find out why it is preferred over a
Several geothermal power plants are in operation in the United States and more are being built since the heat source of a geothermal plant is hot geothermal water, which is “free energy.” An 8-MW
Design a steam power cycle that can achieve a cycle thermal efficiency of at least 40 percent under the conditions that all turbines have isentropic efficiencies of 85 percent and all pumps have
Exhaust gases from the turbine of a simple Brayton cycle are quite hot and may be used for other thermal purposes. One proposed use is generating saturated steam at 110°C from water at 30°C in a
Write an essay on the most recent developments on the two-stroke engines, and find out when we might be seeing cars powered by two-stroke engines in the market. Why do the major car manufacturers
Intense research is underway to develop adiabatic engines that require no cooling of the engine block. Such engines are based on ceramic materials because of the ability of such materials to
In response to concerns about the environment, some major car manufacturers are currently marketing electric cars. Write an essay on the advantages and disadvantages of electric cars, and discuss
The weight of a diesel engine is directly proportional to the compression ratio (W = kr) because extra metal must be used to strengthen the engine for the higher pressures. Examine the net specific
You are designing a closed-system, isentropic expansion process using an ideal gas that operates between the pressure limits of P1 and P2. The gases under consideration are hydrogen, nitrogen, air,
Obtain the following information about a power plant that is closest to your town: the net power output; the type and amount of fuel; the power consumed by the pumps, fans, and other auxiliary
It is well-known that the temperature of a gas rises while it is compressed as a result of the energy input in the form of compression work. At high compression ratios, the air temperature may rise
Compressors powered by natural gas engines are increasing in popularity. Several major manufacturing facilities have already replaced the electric motors that drive their compressors by gas driven
Design a hydrocooling unit that can cool fruits and vegetables from 30 to 5°C at a rate of 20,000 kg/h under the following conditions:The unit will be of flood type, which will cool the products as
Using a timer (or watch) and a thermometer, conduct the following experiment to determine the rate of heat gain of your refrigerator. First make sure that the door of the refrigerator is not opened
Using a thermometer, measure the temperature of the main food compartment of your refrigerator, and check if it is between 1 and 4°C. Also, measure the temperature of the freezer compartment, and
In the search to reduce thermal pollution and take advantage of renewable energy sources, some people have proposed that we take advantage of such sources as discharges from electrical power plants,
The sun supplies electromagnetic energy to the earth. It appears to have an effective temperature of approximately 5800 K. On a clear summer day in North America, the energy incident on a surface
Design a scalding unit for slaughtered chickens to loosen their feathers before they are routed to feather-picking machines with a capacity of 1200 chickens per hour under the following
Design a 1200-W electric hair dryer such that the air temperature and velocity in the dryer will not exceed 50°C and 3 m/s, respectively.
An air cannon uses compressed air to propel a projectile from rest to a final velocity. Consider an air cannon that is to accelerate a 10-gram projectile to a speed of 300 m/s using compressed air,
You are to design a small, directional control rocket to operate in space by providing as many as 100 bursts of 5 seconds each with a mass flow rate of 0.5 lbm/s at a velocity of 400 ft/s. Storage
You have been given the responsibility of picking a steam turbine for an electrical-generation station that is to produce 300 MW of electrical power that will sell for $0.05 per kilowatt-hour. The
Design an experiment complete with instrumentation to determine the specific heats of a gas using a resistance heater. Discuss how the experiment will be conducted, what measurements need to be
Using a thermometer, measure the boiling temperature of water and calculate the corresponding saturation pressure. From this information, estimate the altitude of your town and compare it with the
You are asked to design a heating system for a swimming pool that is 2 m deep, 25 m long, and 25 m wide. Your client desires that the heating system be large enough to raise the water temperature
Find out how the specific heats of gases, liquids, and solids are determined in national laboratories. Describe the experimental apparatus and the procedures used.
A solid normally absorbs heat as it melts, but there is a known exception at temperatures close to absolute zero. Find out which solid it is and give a physical explanation for it.
It is well known that water freezes at 0°C at atmospheric pressure. The mixture of liquid water and ice at 0°C is said to be at stable equilibrium since it cannot undergo any changes when it is
In an article on tire maintenance, it is stated that tires lose air over time, and pressure losses as high as 90 kPa (13 psi) per year are measured. The article recommends checking tire pressure at
The roofs of many homes in the United States are covered with photovoltaic (PV) solar cells that resemble roof tiles, generating electricity quietly from solar energy. An article stated that over its
An electrical-generation utility sometimes pumps liquid water into an elevated reservoir during periods of low electrical consumption. This water is used to generate electricity during periods when
Prepare a report on the heating systems available in your area for residential buildings. Discuss the advantages and disadvantages of each system and compare their initial and operating costs. What
Find out the prices of heating oil, natural gas, and electricity in your area, and determine the cost of each per kWh of energy supplied to the house as heat. Go through your utility bills and
Solar energy reaching the earth is about 1350 W/m2 outside the earth’s atmosphere, and 950 W/m2 on earth’s surface normal to the sun on a clear day. Someone is marketing 2 m × 3 m photovoltaic
Your neighbor lives in a 2500-square-foot (about 250 m2) older house heated by natural gas. The current gas heater was installed in the early 1980s and has an efficiency (called the Annual Fuel
Write an essay on different temperature measurement devices. Explain the operational principle of each device, its advantages and disadvantages, its cost, and its range of applicability. Which device
Write an essay on the various mass‑and volume-measurement devices used throughout history. Also, explain the development of the modern units for mass and volume.
Hot water at 60°C is cooled to 36°C through the tube side of a one-shell pass and two-tube passes heat exchanger. The coolant is also a water stream, for which the inlet and outlet temperatures are
A counter-flow double-pipe heat exchanger with As = 9.0 m2 is used for cooling a liquid stream (cp = 3.15 kJ/kg·K) at a rate of 10.0 kg/s with an inlet temperature of 90°C. The coolant (cp = 4.2
The mass flow rate, specific heat, and inlet temperature of the tube-side stream in a double-pipe, parallel-flow heat exchanger are 2700 kg/h, 2.0 kJ/kg·K, and 120°C, respectively. The mass flow
Air at 18°C (cp = 1006 J/kg·K) is to be heated to 58°C by hot oil at 80°C (cp = 2150 J/kg·K) in a cross-flow heat exchanger with air mixed and oil unmixed. The product of heat transfer surface
A single-pass cross-flow heat exchanger with both fluids unmixed has water entering at 16°C and exiting at 33°C, while oil (cp= 1.93 kJ/kg·K and Ï = 870 kg/m3) flowing at
In a chemical plant, a certain chemical is heated by hot water supplied by a natural gas furnace. The hot water (cp = 4180 J/kg·K) is then discharged at 60°C at a rate of 8 kg/min. The plant
A cross-flow heat exchanger with both fluids unmixed has an overall heat transfer coefficient of 200 W/m2·K, and a heat transfer surface area of 400 m2. The hot fluid has a heat capacity of 40,000
Geothermal water (cp = 4250 J/kg·K) at 75°C is to be used to heat fresh water (cp = 4180 J/kg·K) at 17°C at a rate of 1.2 kg/s in a double-pipe counter-flow heat exchanger. The heat transfer
Consider a water-to-water counter-flow heat exchanger with these specifications. Hot water enters at 95°C while cold water enters at 20°C. The exit temperature of hot water is 15°C
Oil in an engine is being cooled by air in a crossflow heat exchanger, where both fluids are unmixed. Oil (cph= 2047 J/kg·K) flowing with a flow rate of 0.026 kg/s enters the tube side at
The condenser of a room air conditioner is designed to reject heat at a rate of 15,000 kJ/h from refrigerant-134a as the refrigerant is condensed at a temperature of 40°C. Air (cp= 1005
A single-pass cross-flow heat exchanger uses hot air (mixed) to heat water (unmixed), flowing with a mass flow rate of 3 kg/s, from 30°C to 80°C. The hot air enters and exits the heat
Saturated water vapor at 100°C condenses in the shell side of a one-shell and two-tube heat exchanger with a surface area of 0.5 m2and an overall heat transfer coefficient of 2000 W/m2·K.
A shell-and-tube heat exchanger with two-shell passes and 4-tube passes is used for cooling oil (cp = 2.0 kJ/kg·K) from 125°C to 55°C. The coolant is water, which enters the shell side at 25°C
A two-shell passes and four-tube passes heat exchanger is used for heating a hydrocarbon stream (cp = 2.0 kJ/kg·K) steadily from 20°C to 50°C. A water stream enters the shellside at 80°C and
A shell-and-tube heat exchanger is used for cooling 47 kg/s of a process stream flowing through the tubes from 160°C to 100°C. This heat exchanger has a total of 100 identical tubes, each with an
Cold water (cp= 4180 J/kg·K) enters the tubes of a heat exchanger with 2-shell passes and 20-tube passes at 20°C at a rate of 3 kg/s, while hot oil (cp= 2200 J/kg·K) enters the
A shell-and-tube heat exchanger with 1-shell pass and 14-tube passes is used to heat water in the tubes with geothermal steam condensing at 120°C (hfg= 2203 kJ/kg) on the shell side. The tubes
Water (cp = 1.0 Btu/lbm·°F) is to be heated by solar-heated hot air (cp = 0.24 Btu/lbm·°F) in a double-pipe counter-flow heat exchanger. Air enters the heat exchanger at 190°F at a rate of 0.7
By taking the limit as ΔT2 → ΔT1, show that when ΔT1 = ΔT2 for a heat exchanger, the ΔTlm relation reduces to ΔTlm = ΔT1 = ΔT2.
Consider a water-to-water double-pipe heat exchanger whose flow arrangement is not known. The temperature measurements indicate that the cold water enters at 20°C and leaves at 50°C, while the hot
Consider the flow of saturated steam at 270.1 kPa that flows through the shell side of a shell-and-tube heat exchanger while the water flows through 4 tubes of diameter 1.25 cm at a rate of 0.25 kg/s
Consider a closed loop heat exchanger that carries exit water (cp = 1 Btu/lbm·°F and ρ = 62.4 lbm/ft3) of a condenser side initially at 100°F. The water flows through a 500 ft long stainless

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