Hydraulics1. What is the equation for pressure drop in fluid flow through pipe when flow is laminar? (Huiguen Poiuselle Equation) 2. What is the corresponding equation for turbulent flow? (Darcy Wiesbach Equation) 3. You have a 2” pipe line, 2 KM long connecting two points. For a particular flow of water, we experience 2 Kg/cm2 pressure drop. If the diameter of the pipeline is changed to 4”, what will happen to the pressure drop? (New Delta P = (1/32)* Original Delta P) 4. The pressure drop equations for fluid flow through pipeline consider only straight length of pipe. How do we handle pipe fittings? (By taking into account Equivalent Length which is the straight length of the same pipeline required to produce the same pressure drop as that of the original pipeline with the fittings) 5. In what service are globe valves used? Where do we use gate valves? (Globe Valves-Control, Gate Valves- On-Off Service) 6. ???How can we explain the increase in flow through a water tap in the toilet in a household ? 7. ???What is water hammer? How severe is its impact ? 8. What is the Schedule number of a pipe ? ???Where do we use higher schedule pipes and fittings ? (Schedule Number is a indication of the thickness of the pipe) 9. ???What is the function of a control valve ? What is the Control valve Cv ? (Control Valve controls the flow of a fluid through a pipeline. Control Valve coefficient is around 0.66) 10. What is a check valve ? Name a service in your house where a check valve is used ? (Checkvalve are non-return valves which permits flow only in one direction, The valve in the pipeline before the suction of a pump is a check-valve) 11. What is the difference between head and pressure ( explain at a pump discharge ) (H = P / density, at the discharge of a particular pump, the head remains the same for pumping all liquids, whereas the pressure and hence the power requirement increases as the density increases) 12. ???How does a centrifugal pump work? whereas a centrifugal pump need not necessarily give a discharge at all times) 14.. the pump casing gets filled with air. hence the pump will not have the sufficient... Why centrifugal pumps sometime require priming? (Owing to leakage from the pump through the suction nozzle..???. ???In the above case. fill it with the liquid to be pumped. ???Why are variable frequency drives used for motors connected to centrifugal pumps? 25. why is the suction pressure always –ve? (Because the pressure gauge at the suction is a vacuum gauge. ???In the lab test for a centrifugal pump.33m) 19. You have been told that the pump has got an NPSH problem. the suction is negative even if the discharge is blocked.. hence the max reading it shows is 0) 20.N. H prop D2.. What are the 2 NPSHs for a pump? What is the relation? (NPSHA > NPSHR) 18. when it is not running.6 times the original pressure) 24.Pressure above the liquid in the tank + distance between the liquid level and the pump’s suction – vapor pressure of the liquid – frictional losses along the pipe – elevation of the suction nozzle above the ground-level) 16. thus reducing the friction losses or by raising the distance between the pump suction and the liquid level etc) 17.. What is the NPSH of a pump? (Net Positive Suction Head..5 / 13.N2. Why? 21. I have connected a pressure gauge and a barometer in the discharge of a centrifugal pump. Predict the readings in the two meters when the pump fluid is changed from water to glycerin/mercury? (P = H*Density. then slowly open the suction valve and then finally open the discharge valve) 15. (10.to pump the liquid) 23.N3) 22. What are the affinity laws for a centrifugal pump? (Q prop D.13.. What is the difference between a centrifugal pump and a Positive displacement pump? (A positive displacement pump will surely give an output for each stroke. ???How is a centrifugal pump started? How about PD pump? (First. then prime the pump. P prop D3. Pressure becomes 2.. ???What is Bernoulli’s equation? (Pressure Head + Static Head + Velocity Head remains conserved) . How can you improve NPSH? (By increasing the diameter of the pipeline connecting the column and the suction of the pump . ???Why are submersible pumps used in steam condenser services? What is the principle? 26. Calculate the maximum lift possible in a centrifugal pump from the NPSH equation. keep the discharge and suction valve closed. Why is correction factor provided for LMTD? (To account for the deviation from pure countercurrent flow for which the other parameters have been designed) 5. Why are floating head exchangers used? (To accommodate thermal expansion of the tubes when a large temperature difference exists) . ???Why barometric legs are provided for multi-stage ejectors? 30. What is LMTD? (Logarithmic Mean Temperature Difference – Logarithmic is taken as the temperature difference between the fluids varies throughout the HX) 4. ???What is that for convection? (Dittus-Boetus equation. always pure counter-current flow is achieved) 6. paint sprayer) 28. Why a cricket ball swings? Why it does not happen in the case of a golf ball? (OUT OF SYLLABUS)-MUST BE BOUNDARY LAYER SEPARATION Heat Transfer 1.8 * Pr (2/3) ) 3. vapors with non-condensibles.The Velocity head is converted into pressure head in the diffuser section. What is the equation for heat transfer by radiation? (Steffann Boltzmann Equation=> E = sigma * (delta T)4) 2. Nu = Re 0. Name a few applications of Bernoulli’s equation in your household (The gas burner. viscous fluids etc are passed through the pipes while vapors are passed through the shell side) 7. and the velocity head is recovered in the converging section) 29. What are the guidelines of shell side/tubeside allocation of fluids? (Corrosive fluids. Why is the correction factor for double pipe exchangers always 1.0? (Because in doublepipe.27. ???What is the principle of operation of steam ejector? (Bernoulli’s equation. the hose-pipe used for watering in the garden. Hence the area of flow through a single HX is reduced. hence when Q1= 0. and to support the tubes)-they are basically segmented circular metal plates having holes to accommodate the tubes 11. and hence the rate of Heat Transfer also increases. whereas Rating means to check wether an existing HX is suitable for a particular process requirement.8 * Pr (2/3) ) 14. they deposit on the heat exchange surfaces and hence reduce the area available for heat-transfer. What is Dittus-Boetus equation? (Nu = Re 0. whereas for clean services. Also.8.70. we have the freedom to choose the physical parameters and do the necessary calculations for making a HX. (Used when high temperature differential exists. we just need to necessary do the calculations) . When the fluid contains a lot of settle able particulates. then 2 smaller HX can be used. and spacers are tube-sections inserted over the tie-rods to maintain suitable spacing between the baffles) 12. a U-Tube is not recommended as it is difficult for cleaning) 9.6 U.8Q which is 0. this is known as fouling) 16. a triangular pitch or an inverted square pitch is used) 13. here all the physical parameters like the diameter. What is the purpose of using multiple shell exchangers? (When there is a temperature cross occurring in a HX.7 Q. because h prop Q 0. Is the exchanger performing well? (No it is not. Why are tie rods and spacers provided?(Tie-rods are used to hold the baffles in position. but U1 = 0. A heat exchanger with a design U of 200 provides only 120 when the flow through the exchanger is reduced to 70% of the original value. then h1 = 0. What is exchanger fouling? How is it caused? (When the fluid contains settlable solids. hence not working properly) 15.) 10. Where is U-tube bundled exchanger used? Name a service where U-tube is not recommended. usually. and hence the velocity increases. ???What is the difference between heat exchanger design and rating? (In design. the number of tubes to be used in a single HX is also reduced. What are the guidelines for choosing the tube layout for exchanger bundles? For fouling devices or fouling liquids passing through the shell side. a square pitch is preferred as it will easy to clean.8.75 Q) or or or (U prop Q hence U1 prop 0. thickness etc will be mentioned. What is the use of baffles in an exchanger? (To cause a change in the flow pattern of the shell side fluid parallel or cross flow to the tube bundle.7 Q. (Ammonia Synthesis) 2. What is TEMA? What is the significance of TEMA classification of exchangers? (Tubular Exchangers Manufacturers Association.Purge means a part of the output stream from a reactor is taken off so as to prevent the accumulation of contaminants.17. 6. calorie.Recycle means a part of the output stream from a process is send back to the input. Preheating the combustion air by flue gases makes the process more economic as well as a lesser amount ‘\. for eg A represents channel with a fixed tube-sheet. PURGE: . viscosity and density of steam. Latent. 3.Gravity) – 131. Excess Air: Air in excess than stoichiometric quantities that is required for complete combustion is known as excess air. TEMA classifies a HX body into 3 major parts. as a single pass does not result in the complete conversion of a reactant into a product. It is done so as to enhance the conversion. API = (141. Adiabatic Flame Temperature:???Temperature at the flame when a fuel is burnt.5 4. U represents a U-tube bundle etc) 18.hidden Light key and Heavy key. shell and the rear end.5 / Sp. Wet Bulb Temperature: 7. specific steam. water and air 1. K represents a kettle type reboiler. Why are air preheaters provided in furnaces? (To reduce the fuel consumption. No temperature loss to the surroundings takes place OR??? the temperature attained by the flame when the net heat of combustion is required to raise the temperature of the reactants and products. RECYCLE: . Wet Bulb Approach: . the front end. 5. specific heat. The same is the case with the range from 4mA to 20 mA.8. as the pressure drop while passing through the gauge is desired to be kept the lowest possible because. all other terms in the Steffann Boltzmann Equation remains the same. 9. Tube Metal Temperature (TMT) 11. When the fuel composition changes. but a compressor usually cannot handle large volumes of fluid. Radiation. which results in lower radiant heating.. more amount of CO2 will be formed and hence a higher amount of radiant HT will take place and hence the process fluid gains a higher temperature. a drop in pressure will result in expansion of the volume of the fluid being handled. Q = U A delta T For. In an industry. When there is no flow through the pipe. Hence. This is known as live zero.1 Additional heat than required get dissipated in heating up the excess air molecules. 12. Hence when more amount of carbon is present in the fuel given to furnace. Live zero and Dead zero: A pressure gauge which shows a reading from 3psi to 15psi is taken as an example. Hence there is a difference of T3 between both the equations and that shows the difference in heat-recovery. E = sigma * emissivity * (delta T)4 . then it shows the reading 0 which is known as dead zero. Excess Air: Disadvantage 11. Heat carried off by the excess air will not get the same efficiency even if it does some heating in the convective section because For Convection. whereas when the gauge is not functioning properly. hence the adiabatic flame temperature becomes lower. Emissivities: CO2>CO>H2O>N2>O2……. A venturi will be used in rare cases like before the suction of a compressor. 13.2 Emissivities of binary gases are the lowest. usually orifices are used due to the small size and as the maximum and minimum range can be altered. we can differentiate between the 2 situations when there is no flow and when the instrument is not working. 11. Hence the emissivity of O2 and N2 is very low. Why does the flame from an LPG burner appear blue? . 10. the gauge indicates 3psi. water. lead max (almost zero). 29. As the Euro specs increases. this does not happen. Hence.i. 18. melting of ice etc. In the case of a 2-stroke engine. Ponchon Savariat – constant molar overflow. 20. while MS has a sulphur max. drying of wet-clothes etc. It did not consider the fuel modifications so as to improve the engine performance. the temperature of the fluid gets reduced or the vapor pressure of the fluid falls below the suction pressure and hence cavitation can be avoided. height is a function of quality of the column 28. Heat Transfer applications at home: Boiling of milk. Vapor pressure is inversely proportional to the flash point. 16. 19. We emphasize on a high Octane number because. the tendency of self-ignition increases . but for a diesel engine. assumptions 27.e. cooling of water via humudification in mud-pots. By pouring cold water over the pump. viscosity (2-3) etc. Prices of fuel in petrol pumps. hence boiling point temperature decreases. flash point. We make sure that the irr is greater than bank interest rates. as cetane number decreases. so has the engines to be modified as it should be able to compress more and hence utilize the greater octane number of the fuel. 22. McCabe Thiele. lead max. 17. In the case of diesel. Chemical Engineering Apps at homes: above. Mass-Transfer applications at home: leaching during tea making. 26. 23. Octane number generally ranges around 88. if the octane number is lower. Open-steam reduces the pressure. some of the fuel escapes unburnt. 21. whereas in the case of a 4stroke engine. as the octane number increases the engine will be able to compress the vapors to a greater extent and hence derive more energy from the fuel. 25. grinding. freezing of food. . the tendency of self-ignition decrease. mixing etc. BS focuses only on the pollutant levels in the refinery products. 15. there is no spark plug unlike a petrol engine and hence the fuel is meant to be self-ignited and hence a fairly high cetane number is also preferred. Kerosene has specifications like a sulphur max. 24.14. high octane number. recovery. Diameter is a function of quantity. the fuel vapors in the engine catches fire even before the compression stroke is completed and hence the engine won’t be able to exhibit its full efficiency. Steam Distillation 38. August 2008 .e. Surging 39. Flame from LPG Burner appears blue because:37. Darcy Wiesbach equation 41. 31. The lighter component will have to apply a large partial pressure (its vapor pressure) to accomplish the separation and cracking of some of the hydrocarbons may occur and hence. NPV can use different rates everyday 33.if a pump doesn't have a minimum flow it will build up discharge pressure. Propane first gets vaporized in LPG and then Butane. The impeller will start to spin backwards building up pressure again. Equivalent Length 40. 35. This water which can be passed through a heat exchanger gets converted into steam and the same can be used instead of a reboiler. the pump slows down. This can happen with any type of centrifugal pump.1 In crude distillation. IRR is used to check the prof 32. Rate at which we get …………… 34. Pump surging .2 In alcohol/glycol-water separation. if you block the discharge the pump will build up pressure and surging can take place. the cash inflow and cash outflow matches i. NPV is used to compare 2 projects. Pumps & Systems . sometimes some liquid gets retained in the cylinder. where water is the heavier product. open steam is used. We use Open steam in 2 cases:34. 43. NPV = 0. Valves 42. 34. Irr is the discount rate when discounted to the zero year. When this discharge pressure gets high enough the pump cannot overcome it anymore and the water starts to flow backwards. this is due to the reason that the pressure adjustment by the regulator is not sufficient for vaporizing the butane too 36. This cycle of spinning forwards and backwards will repeat itself and will destroy your thrust bearing and destroy your pump.30. When the water starts to flow backwards. The water inside the pump will shift back and forth wreaking havoc with your pump impeller. If the intensity of the shock wave is high. Water hammer is yet another example of conservation of energy and results from the conversion of velocity energy into pressure energy. 48. At ambient temperature. are fully open and have the ability to close instantaneously. the upstream valve closes (this time at the true speed of light). Figure 1 below shows a pump pumping water into a pipe that was empty when the pump started. the kinetic energy due to flow (motion) could be transformed into mechanical energy as the leading edge of the metal column is crushed against the closed valve. if water did not . What events occur as the column strikes the closed. of course). 47. The two valves. located at the pump discharge and the far end of the pipe. The column of water flowing through the pipe also has a perfectly flat leading edge that matches that of the cross sectional ID of the pipe. If this moving column was a column of metal instead of water (hypothetically. it closes at nearly the speed of light and entraps no air ahead of the water column. Since liquids have a low compressibility. 45. Just as flow ceases. physical damage to the system can occur. Oddly enough. This change can produce a shock wave that travels back and forth between the barrier that created it and a secondary barrier. Water hammer (also waterhammer) is a pressure surge that can arise in any pumping system that undergoes an abrupt change in its rate of flow and usually results from pump starts and stops. downstream valve and why does water continue to enter the pipe even though the valve is closed? 49. the opening and closing of valves. we will define water hammer and explore the events that cause it. Neither of these events occurs when water is involved. that same kinetic energy could be used to reverse its direction in the form of a bounce. the column would come to rest and remain motionless at the valve. If its restitution is high enough to prevent crushing. the "entire" metal column would either come to rest or bounce in the opposite direction. which seems to suggest it is slightly compressible.0000034 percent. the resulting pressure energy tends to be high. and the water column is completely isolated between the two valves. regardless of the pressure. it can be more of a concern in low pressure applications. but the larger the volume. Depending on its coefficient of restitution (its ability to avoid permanent damage). Water is a nearly non-compressible liquid. Regardless of the outcome. valves and other fittings are entirely inelastic and no volume change can occur.44. We will also try to gain perspective on the additional pressure it generates. The pipe. the easier it is to see the effect. or water column separation and closure. 50. If this occurred. For example. flow into the pipe continues for the next few milliseconds. That seems pretty small. These abrupt changes can cause all or part of the flowing water column to undergo a momentum change. 46. 1-psi will decrease its volume by about 0. When the leading edge of the water column reaches the downstream valve. In part one of this two-part column. Even though the leading edge has struck the closed valve. a couple of things could occur. Perhaps the best way to visualize this action is to start with a hypothetical example. say 40. Slip Increases Directly with Pressure Directly with Clearance . which is primarily nitrogen (78 percent) and oxygen (21 percent). if slip occurs. fish could not survive! Dissolved air composes about 2 percent of a given volume of unprocessed water. sea level would be roughly 100-ft higher than its current level! At very high pressures. Slip Slip and Efficiency A major effect on positive displacement pump performance is the loss in flow due to slip. and adds substantially to its compressibility. Pump performance is dependent on the slip which occurs in a pump. the cavity will also be partly filled with fluid flowing back through the pump clearances from the outlet side. This cavity can be filled with fluid from the inlet line in normal performance. The expanding cavity on the inlet side of a positive displacement pump creates a low pressure area that asks to be filled with fluid. But.000-psi. Otherwise. its compressibility is increased to about 10 percent. However. most water is not just water-it also contains air.compress. 5 MMPTA. a Coker which gives more flexibility to the operations is also being introduced. In the petrochemical complex. there will be ethylene unit. a hydro-treater is introduced. The expansion and revamp aims at producing 80% EURO-4 and 20% EURO-5 fuel. MRPL is expanding from 11. propylene unit etc. It is at present producing 80% EURO-3 and 20% EURO-4 fuel. . 52. It’ll be also introducing an FCC unit and a subsequent propylene recovery unit too . the CDU and VDU is being completely replaced having higher crude handling capacities..Inversely with Viscosity When actual flow (Qact) in pump is greater than theoretical flow (Qth) then negative slip occurs.82 MMPTA to 15 MMPTA. BPCL at present is expanding to the capacity of 15.. In the Integrated Refinery Expansion Project.5 MMPTA from the present 9. 53... It has already commissioned its CDU and VDU units. It is also introducing petrochemical units for propylene derivatives and phenol derivatives. 51. Slip is the phenomenon which occurs in the motor due to which it is not able to rotate at the maximum speed. when this cool air comes in contact with the body. The flange to flange distance in the body of a Gate valve is smaller in comparison to that of a Globe valve. then back flow of liquid from the discharge to the suction occurs and the flow again reverses causing havoc to the impeller as well as the pump. When these 2 terms becomes equal. when a substance undergoes compression a decrease in the temperature occurs which will lead to the cooling of Freon. Whereas in the case of an Air cooler which is used in North-India where the humidity is around 20%. 58. Surging occurs in compressors and only for compressible fluids. It is a rule of thumb that in a pipeline containing a control valve. This is because the vapour pressure of water at room temperature is 0. 61. There is sufficient driving force between the ambient air and the water and hence the water vaporizes into the air taking latent heat from the air and hence the air gets cooled. hence if the compressor is operated at a flow-rate to the left or right of the point of maximum head. 62. Cv is used to rate the control valves. connecting 2 columns. the H vs Q curve is the shape of an inverted U. hence it can be identified. and thereby. 55. which is less than 1 atm and hence vacuums. Relative humidity is the ratio of actual humidity to the saturation humidity. LNG 63. 57. BWG. there exists a driving force and the sweat vaporizes into the air taking latent heat from the body and hence we feel cool. the valve later on will not stop the flow even when tight shut. it expands and the air gets cooled. Equivalent Length is the net straight length of a pipe after incorporating the effects of various fittings and bends along the pipeline. 59. 50% . Unlike pumps. 56. Shut off point of a pump signifies the head at zero flow rate or when the discharge is completely closed. The control valve coefficient is defined as the flow in gallons per minute of water through a valve 2 when the pressure drop is 1 kg/cm . humidification of air takes place. The principle of an AC is dehumidification. for compressors. This evaporated sweat precipitates and forms water droplets which flow out of the AC.60% of the pressure drop in the line is given by the valve for only then will a slight cange in the valve position bring in a significant change in the flow of fluid. there takes place NIL mass transfer as the driving force is zero because the surrounding air is also saturated with high humidity level. then Relative Humidity = 100 and therefore precipitation of the moisture in air takes place resulting in rainfall. leakage will be there. Saturation humidity is the maximum humidity in air beyond which water vapour cannot enter the air at a particular temperature. In the equation of . The suction pressure of a centrifugal pump taking lift always shows negative and still the pump is able to lift the liquid. A Gate valve cannot be used for control purpose as the pressure drop during the flow through valve causes heating of the valve parts and gradual wearing off of the parts.54.95 atm gauge.05 atm absolute and hence 0. When the cold Freon comes into contact with the warm ambient air. In Kerala when the body is covered with sweat. According to Joules Thompson effect. 60. We always keep the discharge of a centrifugal pump closed during starting to develop the sufficient head. Bernoulli’s equation – steam jet ejector-barometric leg 65.htm .NPSH. Hence on substituting in the equation. we get NPSH = . LNG 67. When the water is boiling. the pump suction elevation above the ground level. A PD pump has a by-pass valve 69. abouthttp://www.75 atm and hence the net NPSHa is positive and hence the pump is able to lift the liquid. Directors . CEMP.2 – (. 68.0.matche. 64. NPV. IEMP 70. thereby the pump will be unable to lift. LPG. we can neglect the friction losses in the pipe.95) + 0 = 0.0.com/EquipCost/Index. IRR 66.2 atm gauge. its vapour pressure will be 1 atm and hence 0 atm gauge and hence the net NPSHa will become negative. The suction pressure will be around -0.