单选题Generating tubes in waste heat boilers are finned to （）.Areduce gas flow turbulenceBprevent exhaust gas corrosionCincrease the rate of combustionDincrease the rate of heat transfer
单选题
Generating tubes in waste heat boilers are finned to （）.
A
reduce gas flow turbulence
B
prevent exhaust gas corrosion
C
increase the rate of combustion
D
increase the rate of heat transfer
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5 The directors of Blaina Packaging Co (BPC), a well-established manufacturer of cardboard boxes, are currentlyconsidering whether to enter the cardboard tube market. Cardboard tubes are purchased by customers whoseproducts are wound around tubes of various sizes ranging from large tubes on which carpets are wound, to smalltubes around which films and paper products are wound. The cardboard tubes are usually purchased in very largequantities by customers. On average, the cardboard tubes comprise between 1% and 2% of the total cost of thecustomers’ finished product.The directors have gathered the following information:(1) The cardboard tubes are manufactured on machines which vary in size and speed. The lowest cost machine ispriced at $30,000 and requires only one operative for its operation. A one-day training course is required in orderthat an unskilled person can then operate such a machine in an efficient and effective manner.(2) The cardboard tubes are made from specially formulated paper which, at times during recent years, has been inshort supply.(3) At present, four major manufacturers of cardboard tubes have an aggregate market share of 80%. The currentmarket leader has a 26% market share. The market shares of the other three major manufacturers, one of whichis JOL Co, are equal in size. The product ranges offered by the four major manufacturers are similar in terms ofsize and quality. The market has grown by 2% per annum during recent years.(4) A recent report on the activities of a foreign-based multinational company revealed that consideration was beinggiven to expanding operations in their packaging division overseas. The division possesses large-scale automatedmachinery for the manufacture of cardboard tubes of any size.(5) Another company, Plastic Tubes Co (PTC) produces a narrow, but increasing, range of plastic tubes which arecapable of housing small products such as film and paper-based products. At present, these tubes are on average30% more expensive than the equivalent sized cardboard tubes sold in the marketplace.Required:(a) Using Porter’s five forces model, assess the attractiveness of the option to enter the market for cardboardtubes as a performance improvement strategy for BPC. (10 marks)
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
What is the most usual reason for the fresh water-sea water heat exchanger fouling in the sea side?A.lube oil sludge accumulating in itB.dirt and scale etc , formed on the surfacesC.deformation of the tubes and the shell or the platesD.lube oil leakage into sea-water side
The maximum pressure developed by a waste heat boiler is determined by the main engine exhaust ______.A.gas compositionB.gas temperatureC.pressureD.timing
A bypass line provided around a waste heat auxiliary boiler in a diesel engine exhaust system, may be used to avoid boiler ______.A.corrosion at low engine loadsB.erosion at high engine loadsC.overload at high engine loadsD.scaling at all exhaust temperatures
单选题Before shutting off the fuel supply to stop a medium or high–speed diesel engine, why is it necessary to allow the engine to idle for a few minutes?（）ATo prevent internal damage form local overheatingBTo ensure the fuel nozzles are flushed cleanCTo clear the smoke stackDTo let the waste heat boiler reduce its rate of steam generation
单选题Which of the following items is necessary for all waste heat boiler installations, regardless of design or manufacturer? （）AControl of evaporationBA separate means to prevent feed-water contaminationCPower circulating pumpDSuper-heater
单选题Which of the diesel engine cylinder liners listed has internal cooling water passages?（）AInternally finned linerBExternally finned linerCWet linerDIntegral water-jacket liner
单选题An exhaust gas bypass is installed on a waste heat boiler in order to （）.Abypass exhaust gas at high loads to prevent excessive back pressureBbypass a portion of the exhaust gas at peak loads for better efficiencyCrecycle exhaust gas to the turbochargerDminimize moisture condensation in the boiler gas passages at low loads
单选题The diesel engine exhaust gas bypass, as fitted with some waste heat boilers, is installed to （）Aprevent engine back pressure at heavy loadsBincrease total engine efficiency at low loadsCprevent boiler corrosion at low engine loadsDimprove engine fuel consumption at any load
单选题If the jacket water temperature of an operating diesel engine suddenly rises above normal, the cause can be attributed to （）.Aan overfilled expansion tankBexcess chromate treatment of the jacket waterCa clogged raw water sea suctionDcavitation erosion of the heat exchanger tubes
单选题Waterside scale in a fire-tube boiler may cause （）.Aincreased heat transferBfireside erosionChigh steam demandDoverheated tubes
单选题The rate of heat transfer between the hot and cold fluids passing through a shell-and-tube type heat exchanger will （）.Aremain constant along the tubes lengthBbe greatest in a single pass counter flow heat exchangerCremain constant throughout the heat exchangerDvary from section to section through out the heat exchanger
单选题The purpose of designing some waste heat boilers with sinuous fire tubes, is to（）Aincrease exhaust gas velocity through the boilerBreduce accumulations of carbon deposits on the heat transfer surfacesCeliminate exhaust gas pulsations and noiseDincrease the rate of heat transfer to the waterside
单选题Diesel engine waste heat boiler construction is usually of the fire-tube or（）Acyclone furnace boiler typeBdry back boiler typeCwater-tube typeDcritical circulation boiler type
单选题Generating tubes in waste heat boilers are finned to （）.Areduce gas flow turbulenceBprevent exhaust gas corrosionCincrease the rate of combustionDincrease the rate of heat transfer
单选题Which of the following statements concerning fire-tube boilers is correct?（）ACombustion gases flow through the tubesBFlames impinge on the tubesCCombustion occurs in the tubesDWater flows through the tubes
单选题The maximum pressure developed by a waste heat boiler is determined by the main engine exhaust （）.Agas compositionBgas temperatureCpressureDtiming
单选题Exhaust pipes for separate diesel engines can be combined only when （）Aspace limitations prevent separately run pipesBthe engines are small auxiliary unitsCthey are arranged to prevent gas backflow to each engineDa waste heat boiler is installed
单选题Fins are installed on the fireside of water-tubes used in waste boiler to（）Adecrease the velocity of gases flowing past the tubesBincrease the rate of heat transferCreduce accumulations carbon depositsDdirect the flow of gases
单选题The heat used to change a liquid to a vapor is called （）.Alatent heat of fusionBlatent heat of vaporizationCspecific heat of vaporizationDlatent heat of the gas
单选题In motor ship, （） is often used to recover some of the heat carried in the exhaust gases from the main engine.Aan diesel oil heaterBa waste heat boilerCa fresh water generatorDall the above
单选题Fins are installed on the generating tube surfaces in waste heat boilers to （）.Aprevent soot fires in the exhaust systemBprevent exhaust gas erosion of the tubesCincrease the velocity of exhaust gas flowDincrease the rate of heat transfer
单选题Which of the following equipment can not be used for the waste heat recovery of the M/E to further improve its thermal efficiency?（）AM/E turbochargerBexhaust gas boilerCincineratorDfresh water generator
单选题The PRIMARY function of a waste heat boiler is to （）.Areduce engine exhaust noiseBreduce engine back pressureCrecover heat which otherwise would be lostDincrease turbocharger efficiency
单选题To avoid impingement attack, care must be taken with the water （） through the tubes of the heat exchangers.AtemperatureBvelocityCdensityDviscosity
单选题A waste heat boiler is installed on some diesel propelled vessels to （）.Aprovide steam for emergency propulsionBprovide steam for the turbo-generatorCheat the waste water tanksDsteam for warming engines
单选题A SECONDARY function of a waste heat boiler is to （）.Areduce engine exhaust noiseBreduce engine back pressureCincrease engine cycle efficiencyDincrease turbocharger efficiency