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单选题
The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.
A
remain constant along the tubes length
B
be greatest in a single pass counter flow heat exchanger
C
remain constant throughout the heat exchanger
D
vary from section to section through out the heat exchanger
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更多 “单选题The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.A remain constant along the tubes lengthB be greatest in a single pass counter flow heat exchangerC remain constant throughout the heat exchangerD vary from section to section through out the heat exchanger” 相关考题
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People with circulatory problems often have cold feet and hands, because heat moves between the ( ) and the ( ) as the blood flows.
A、headB、heartC、bloodD、cells
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HTTP 是指：A.HyperText Transfer ProtocolB.Hyperlink Text Transfer ProtocolC.Hot Text To ProtocolD.Hyperlink Text To Post
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第二组The only attention that heat exchanger should require is to ensure that the heat transfer surfaces remain substantially clean and the flow passages generally clear of obstruction. Indication that undue fouling is occurring is given by a progressive increase in the temperature difference between the two fluids, over a period of time, usually accompanied by a noticeable rise in pressure loss at a given flow.Fouling on the sea-water side is the most usual cause of deterioration in performance. The method of cleaning the sea water-side surfaces depends on the type of heat exchanger. With shell-and-tube heat exchangers, the removal of the header covers or, m the case of the smaller heat exchangers, the headers themselves, will provide access to the tubes. Obstructions, dirt, scale etc., can then be removed, using the tools provided by the heat exchanger manufacturer. Flushing through with fresh water is recommended before a heat exchanger is returned to service. In some applications, such as piston oil cooling, progressive fouling may take place on the outside of the tubes. Most manufactures recommend a chemical flushing pr6cess to remove this in situ~ without dismantling the heat exchanger.Plate heat exchangers may be cleaned by unclamping the stack of plates and mechanically cleaning the surface of each plate as recommended by the manufacturers. The plate seals may require replacement from time to time and here the manufacturers instructions should be closely followedBy which of the following indication, can we conclude that the lube oil-sea water heat exchanger is unduly fouled?A.the heat exchanger lube oil inlet temperature loweringB.the heat exchanger sea-water outlet pressure riseC.the heat exchanger temperature difference between lube oil and sea water increasingD.the heat exchanger pressure difference between sea water inlet and outlet decreasing
考题
Which of the following modes of heat transfer does NOT require any physical contact between a warmer and a cooler substance?A.RadiationB.ConductionC.Natural convectionD.contact directly
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共用题干
第一篇Heat and HealthExtremely hot weather is common in many parts of the world.Although hot weather just makes most people hot,it can cause medical problems and death.Health experts say that since the year 1900,extremely hot weather has killed more people in the United States than any other natural event.One year一the unusually hot summer of 1980一heat caused about 1,700 deaths in the United States.In 1995,more than 600 people died in a similar heat wave in one city一Chicago.To measure extreme heat,government weather experts have developed the Mean Heat Index.It measures the average of how hot it is felt all day on an extremely hot day.Experts say it is the total heat of a hot day or several hot days that can affect health.Several hot days are considered a heat wave.Experts say heat waves often become deadly when the nighttime temperature does not drop much from the highest daytime temperature.The most common medical problem caused by hot weather is heat stress.It is also least severe.For most people,the only result of heat stress is muscle pain.The pain is a warning that the body is becoming too hot. Doctors say drinking water will help the pain disappear after the body again has the right amounts of water and salt.For some people, however,the result is much more serious.For example,doctors say some people face a greatly increased danger from heat stress.These people have a weak or damaged heart,high blood pressure,or other problems of the blood system.Severe heat can help cause a heart attack or stroke.Health experts say this is the most common cause of death linked to hot weather. A heat wave is a period of time during whichA:the weather is much better than usual.B:the nights are much longer than usual.C:the weather is much hotter than usual.D:the days are much longer than usual.
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共用题干
第一篇Heat and HealthExtremely hot weather is common in many parts of the world.Although hot weather just makes most people hot,it can cause medical problems and death.Health experts say that since the year 1900,extremely hot weather has killed more people in the United States than any other natural event.One year一the unusually hot summer of 1980一heat caused about 1,700 deaths in the United States.In 1995,more than 600 people died in a similar heat wave in one city一Chicago.To measure extreme heat,government weather experts have developed the Mean Heat Index.It measures the average of how hot it is felt all day on an extremely hot day.Experts say it is the total heat of a hot day or several hot days that can affect health.Several hot days are considered a heat wave.Experts say heat waves often become deadly when the nighttime temperature does not drop much from the highest daytime temperature.The most common medical problem caused by hot weather is heat stress.It is also least severe.For most people,the only result of heat stress is muscle pain.The pain is a warning that the body is becoming too hot. Doctors say drinking water will help the pain disappear after the body again has the right amounts of water and salt.For some people, however,the result is much more serious.For example,doctors say some people face a greatly increased danger from heat stress.These people have a weak or damaged heart,high blood pressure,or other problems of the blood system.Severe heat can help cause a heart attack or stroke.Health experts say this is the most common cause of death linked to hot weather. What can people learn from the Mean Heat Index?A:The average temperature of an extremely hot day.B:The highest temperature of an extremely hot day.C:The lowest temperature of an extremely hot day.D:The nighttime temperature of an extremely hot day.
考题
共用题干
第一篇Heat and HealthExtremely hot weather is common in many parts of the world.Although hot weather just makes most people hot,it can cause medical problems and death.Health experts say that since the year 1900,extremely hot weather has killed more people in the United States than any other natural event.One year一the unusually hot summer of 1980一heat caused about 1,700 deaths in the United States.In 1995,more than 600 people died in a similar heat wave in one city一Chicago.To measure extreme heat,government weather experts have developed the Mean Heat Index.It measures the average of how hot it is felt all day on an extremely hot day.Experts say it is the total heat of a hot day or several hot days that can affect health.Several hot days are considered a heat wave.Experts say heat waves often become deadly when the nighttime temperature does not drop much from the highest daytime temperature.The most common medical problem caused by hot weather is heat stress.It is also least severe.For most people,the only result of heat stress is muscle pain.The pain is a warning that the body is becoming too hot. Doctors say drinking water will help the pain disappear after the body again has the right amounts of water and salt.For some people, however,the result is much more serious.For example,doctors say some people face a greatly increased danger from heat stress.These people have a weak or damaged heart,high blood pressure,or other problems of the blood system.Severe heat can help cause a heart attack or stroke.Health experts say this is the most common cause of death linked to hot weather. Muscle pain in hot weather means that your body needsA:more exercise. B:more water.C:less oxygen. D:less sugar.
考题
The purpose of mentioning the Weddell Sea is___________.A.to give an example of cold-water salinity
B.to point out the location of deep waters
C.to make a comparison between hot-water salinity and cold-water salinity
D.to show that the water in the Weddell Sea varies in salinity from place to place
考题
单选题The spreading of fire as a result of heat being carried through a vessels ventilation system, is an example of heat transfer by （）.A
conductionB
convectionC
radiationD
windage
考题
单选题One advantage of dry cylinder liners used in a diesel engine is the（）A
lower thermal expansion rates than wet linersB
greater heat transfer rate than wet linersC
greater wear resistance than wet linersD
procedure to replace dry liners is simpler than for wet liners
考题
单选题The rate of heat transfer in a water-tube auxiliary boiler can be increased by （）.A
operating the boiler at less than normal water levelB
installing fins on the firesides of water-tubesC
increasing the amount of excess air to the burnersD
treating the boiler water with chemical oxygen scavengers
考题
单选题However fast or slow the combustion rate, it is still a （） between carbon, hydrogen, sulphur and oxygen that releases heat.A
physical deformationB
state exchangeC
chemical reactionD
coalescence
考题
单选题Which of the following modes of heat transfer does NOT require any physical contact between a warmer and a cooler substance?（）A
RadiationB
ConductionC
Natural convectionD
All of the above
考题
问答题Practice 1 Heat loss by sweating depends on the fact that when a liquid evaporates, it absorbs an enormous quantity of heat from its surroundings. Therefore, when I am of sweat evaporate, a great deal of heat is absorbed from the surface of the body in contact with it. 1______ 2______ The first is the amount of movement of air surrounding the body. The second is the amount of water vapor in the air that surrounds the body. 3______ For this reason, sweat evaporates very rapidly on windy days, and the rate of heat loss by sweating is much more than on a still day. This accounts for the fact that hot still days are much less comfortable than hot windy days. In contrast, the sweat evaporates very rapidly on hot windy days, and cools the body quickly and effectively. 4______ When air is carrying the maximum amount of water vapor that it can hold, it is said to be 100% saturated with water vapor. The relative humidity of the air is said to be 100%. Under these conditions the air cannot carry any water, so no water can evaporate. When the relative humidity is high, therefore, sweat cannot evaporate. Instead, it forms large drops and runs off your skin without cooling you. 5______ It is obvious that under these conditions, evaporation will be much more rapid. Therefore, sweating will be much more effective as a method of losing heat from the body. On a hot dry day, sweat evaporates as soon as it is formed, and you feel reasonably cool even though the temperature of your environment is very high.[A] When the air is very dry and carries no water at all, the relative humidity is said to be 0%.[B] The second factor is the amount of water vapor in the air－the humidity.[C] Hot windy days are much more comfortable than hot still days.[D] This heat transfer occurs even if the environment is hotter than the body.[E] When air moves over the surface of water, the amount of evaporation is greatly increased.[F] You might expect the highest incidence of a heat stroke when the maximum temperature is 100 and humidity is 50%.[G] Two factors affect the rate of evaporation of sweat, and therefore the effectiveness of sweating as a method of cooling the body.
考题
单选题Which of the statements listed concerning heat transfer is correct?（）A
Heat is always transferred at a constant rateB
Heat transfer rate increases as temperature difference increasesC
The rate of heat transfer is not affected by temperature differenceD
The high temperature region is known as a heat sink
考题
单选题The rate of heat transfer from a hot region to a cold region is affected most by the （）.A
size of the heat sinkB
temperature difference between the regionsC
size of the heat sourceD
total heat of the system
考题
单选题Which of the following statements is correct concerning heat transfer?（）A
Heat is given off from a high temperature region known as a heat sinkB
Heat transfer rate is affected most by the size of the heat sink involvedC
Heat transfer rate is affected most by the temperature difference between the heat source and the heat sinkD
Heat transfer by radiation will occur only by mass motion of a fluid substance
考题
单选题The purpose of designing some waste heat boilers with sinuous fire tubes, is to（）A
increase exhaust gas velocity through the boilerB
reduce accumulations of carbon deposits on the heat transfer surfacesC
eliminate exhaust gas pulsations and noiseD
increase the rate of heat transfer to the waterside
考题
单选题Generating tubes in waste heat boilers are finned to （）.A
reduce gas flow turbulenceB
prevent exhaust gas corrosionC
increase the rate of combustionD
increase the rate of heat transfer
考题
单选题Scale accumulation on evaporator heat exchange surfaces （）.A
increases brine densityB
increases distillate salinityC
reduces metal corrosionD
reduces heat transfer
考题
单选题Fins are installed on the generating tube surfaces in waste heat boilers to （）.A
prevent soot fires in the exhaust systemB
prevent exhaust gas erosion of the tubesC
increase the velocity of exhaust gas flowD
increase the rate of heat transfer
考题
单选题Physical exertion on the part of a person who has fallen into cold water would（）.A
be the best thing to try if there was no rescue in sightB
increase survival time in the waterC
increase the rate of heat loss from the bodyD
not affect the heat loss from the body
考题
单选题Sacrificial zinc anodes are used on the saltwater side of diesel engine heat exchangers to（）.A
reduce electrolytic action on heat exchanger metalsB
keep heat transfer surfaces shiny and cleanC
prevent rapid accumulation of marine growthD
provide a protective coating on heat exchanger surfaces
考题
单选题Hot air can hold（）.A
less moisture than cold airB
more moisture than cold airC
the same amount of moisture as cold airD
moisture independent of air temperature
考题
单选题We find that some birds _____ twice a year between hot and cold countries.A
transferB
commuteC
migrateD
emigrate
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