Experts

Heat Transfer

Heat Transfer by Jim Grant, DuPont

Jim Grant is a senior consultant for DuPont, Wilmington, Del. He has worked in the Engineering Department of the company for the past 24 years, the last 16 providing internal support for heat and mass transfer applications at plants worldwide. He is an adjunct faculty member of the University of Delaware and teaches internal company courses on heat transfer and distillation. He represents DuPont at Heat Transfer Research Inc., an industry consortium performing full scale heat transfer research and software development, and is active on its technical committee.

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Solvent recovery exchanger type
What type of heat exchanger is most efficient for solvent recovery mounted on the reactor, horizontal or vertical?
Category: Heat Transfer

Thermal properties for heat transfer fluids
I work for a heater manufacturer and often have projects to work on requiring power calculations for all manner of substances. I am trying to find the typical thermal properties for heat transfer fluids such as Santotherm and Therminol. The manufacturers web sites don't seem to have this information. I am interested in the typical specific heat capacity for these fluids, can you help or point me to a site which has this information?
Category: Heat Transfer

Controlling melting time, temperature
Please recommend the best and fastest method of controlling the melting of beef fat in a thermal oil, jacketed vessel. The fat melts at approx 70ºC and must not go over 90ºC. There are two 3-Kw elements. The controller is basically a "on/off" control, turning the elements on when under temperature and turning them off when set point is reached. Would you measure the fat or the oil? If we measure the fat, melting time is drastically reduced, but a huge overshoot is experienced. Oil control is better, but the melting time is increased.
Category: Heat Transfer

Multi-passing heat exchanger tube criteria
What are the main criteria for multi-passing heat exchanger tubes? What is the latest useful software to complete design of heat exchangers?
Category: Heat Transfer

Heat tracing calculations
What is the best method to calculate and design piping for a heat tracing fluid such as petrotherm?
Category: Heat Transfer

Coefficient for a externally wound coil
What will be approximate heat transfer coefficient for a externally wound coil for a heating vessel? (Hot oil is circulated in the coil to boil fluid inside the vessel.)
Category: Heat Transfer

Use of methanol in a closed loop geothermal heat pump application
We have a construction project where the owner is requiring the use of methanol for their new school construction. The geothermal loop subcontractor states they use methanol all the time, with no problems. However, as a buyer for the material for this project, I am running into all kinds of hurdles for pumps, piping, gaskets and glycol feed systems. What can you tell me about the use of methanol in a closed loop geothermal heat pump application?
Category: Heat Transfer

Closed-loop technology in refineries
Can you brief me on air and/or fluid handling systems in refineries? I'm looking into a new closed-loop technology and would like to better understand (in general) how these systems get intergrated into refineries.
Category: Heat Transfer

The variation of pressure drop
How does the air-side pressure drop in a air-fuel heat exchanger vary as a function of altitude and temperature?
Category: Heat Transfer

Silica-based scale
What are the most effective or simple methods to remove silica-based scale from heat exchangers?
Category: Heat Transfer

Reference for heat transfer properties
Where would I find a reference for heat transfer properties of boiler tubes online, or otherwise? This would be of great help in my design for a heating system.
Category: Heat Transfer

Internal valve temperature
I have a water cooled check valve mounted on the end cover of a gas turbine. The valve is for use with liquid fuel, however, during natural gas operation there is no liquid fuel flowing through the valve, just water circulating through the jacket to keep it cool. How would I determine the temperature of the internals of the valve? I know the water temperatures (in and out), and I know the surface temperatures (in and out) of the check valve. Would the log/mean temperature equation be the right approach?
Category: Heat Transfer

Shaft temperature calculation
If one pump is handling oil at temp 320ºC and the bearing housing temperature is around 82ºC. I want to calculate the shaft temperature that is rotating at bearing support. How do I calculate the heat transfer if the shaft is made up of steel 4140?
Category: Heat Transfer

Still-air solar radiation exposure temperature
When an object is exposed to solar radiation in still air, how does one calculate the maximum temperature it will attain? I've seen API RP521 making reference to a maximum temperature of ~71°C for piping and I was wondering how they arrive at that figure.
Category: Heat Transfer

Cooler pipe design
How do you design an after cooler pipe for a two-stage, reciprocating compressor with aluminum fins?
Category: Heat Transfer

Reboiler design differences
What is the major area to consider while design a reboiler? How different is it from normal heat exchanger designs? Are there Web sites I can reference?
Category: Heat Transfer

Oil flow calcuations
I have a new oil-to hot water heat transfer (with 1 million BTUH input system), with an oil input of 450ºF and a hot water output at 350ºF. I need to calculate the maximum oil flow needed when 8,000 BRUH for 1 sq. ft. of HS and the maximum water flow output at 350ºF.
Category: Heat Transfer

Correct percentage of allowable tubes
What percentage of tubes can allowably be plugged in a shell and tube heat exchanger?
Category: Heat Transfer

Heat transfer loss estimation
I have a finned tube heat exchanger. The tube side is supplied with cooled condensate. The shell side is cooling gaseous hydrogen and is contaminated with lubricating oil. What is the potential heat transfer loss, in a range?
Category: Heat Transfer

Evaporative cooling calculation
I am a former DuPonter from Singapore and now working with a new company. I would like to know the design and process calculations for evaporative cooling using spray nozzles on top of a belt conveyor carrying rubber at 450ºF.
Category: Heat Transfer

Flammable thermic fluids
Can thermic fluid systems catch fire if the fluid becomes contaminated and its flash and fire point become lower?
Category: Heat Transfer

Condensing reflux designs
Can you recommend some published references that discuss vertical shell-side condensing reflux designs? I have read articles that discussed reflux condensers condensing inside the tubes, but I have not come across any articles that discuss vertical condensing outside the tubes. This type of heat exchangers is common for overhead condensers in distillation columns under vacuums and also for vent condensers in tanks and drums. Even though non-condensibles are present and the vapor flow direction is up while the condensed liquid is down, there should not be any flooding issues since the condensation is outside the tubes. Are the heat transfer coefficients correlations for condensation inside the tubes applicable for this type of heat exchanger designs? What is the approximate overall heat transfer coefficient of this type of reflux condensers assuming some non-condensibles are present?
Category: Heat Transfer

Heat tranfer coefficient calculations (outside and inside areas)
I work with concentric heat exchangers, specifically a double-pipe unit with hot water flow in the inner tube and the cold water flow in the annulus. I calculate the flow rates and temperatures for the hot and the cold water. There is a plastic element inside the inner tube to enhance the heat transfer and I want to compare the heat transfer in the heat exchanger both with and without the element. What is the equation to calculate the overall heat transfer coefficient and what is different between based on outside area or inside area? How can I calculate heat transfer coefficient inside the tube and also outside the tube (in the annulus)?
Category: Heat Transfer

Heat transfer coefficients
I am considering heating a copper plate with a food-grade, heat transfer fluid, but am having trouble finding data about heat transfer coefficients. What is the heat transfer coefficient (W/m²K) between a turbulent oil flow and a copper plate?
Category: Heat Transfer

Methanol use for a closed-loop geothermal heat pump
We have a construction project where the owner is requiring the use of methanol for their new school construction. The geothermal loop subcontractor states they use methanol all the time with no problems. However, as a buyer for the material for this project, I am running into all kinds of hurdles for pumps, piping, gaskets and glycol feed systems. What can you tell me about the use of methanol in a closed-loop geothermal heat pump application?
Category: Heat Transfer

Condenser accumulator arrangements
I am in charge of overseeing the operation of several distillation/fractionation towers in my refinery. I have noticed that in some towers the overhead condensers are at ground level, while the accumulators are at a higher altitude. I know that this configuration is acceptable and even recommended where total condensing is required. In fact, some towers have no accumulators at all and the condensers are big enough to maintain a level and adequate volume for both product and reflux. However, in the towers in question, the condensing is partial. The accumulators have a vapor product (which control the accumulator/tower pressure) and a distillate product (on level control). Shouldn't the condensers be at a higher altitude than the accumulator? What is the importance of the location/configuration?
Category: Heat Transfer

Heat transfer properties of oil and steam
Please explain which has the most effective and efficient heat transfer properties between heating: oil or steam? The project I am working on currently uses steam at 850 Kpa and heats a chamber through a steel-jacketed system. The process needs to heat as quickly as possible and needs to obtain a temperature around 136ºC. The process is for sterilization and uniformed heating is not important.
Category: Heat Transfer

Fin tube heat absorbtion
I am designing a containment structure (box) approximately 5 ft (H) x 3 ft (W) x 8 in (L) that will be exposed to direct sunlight. I would like to internally include a heat exchanger built with fin tubes that would remove/absorb the heat in the container in the box itself. I have seen calculations from fin tube suppliers that can relate the amount of Btus being dissipated in a foot of fin tube, but not a calculation for the amount of heat that could be absorbed in a contained environment. When I see that a foot of fin tube might dissipate 900/1,100 Btu hours, is there a simple calculation or factor that could be applied to determine what that same foot of fin tube would absorb? In other words, if a foot dissipates 900 Btus, absorbtion might be 80% or 90% of the 900 Btu's in that closed container. I would appreciate any information you can provide.
Category: Heat Transfer

Vendors information for humidified gas/flue gas interchangers
I am looking for potential vendors/types for a humidified gas/flue gas interchanger for cooling flue gas from 1,000ºF to 900ºF and heating humid gas from 200ºF to 940ºF for total duties of 0.13mm Btu/h. We have purchased Sumitomo plate-fin exchangers in the past, but have had mixed results with sort life from thermal cycling. Would you recommend any other types, potential vendors or resources to look for alternatives? I also have a downstream heat exchanger that further cools flue gas to 200ºF by making tempered water at 250ºF.
Category: Heat Transfer

Parallel heat plate design, code information
I want to know how to design a parallel plate heat exchanger. I also need to know what API code, IRB code and ISO14000 code is. I have been in production for the last five years and want to get involved in consultant work.
Category: Heat Transfer

Superheater temperatures
The superheater cools gas from 620ºC to 440ºC and, in the process, superheats steam from 225ºC to 400ºC. Eight tubes in the superheater developed leaks and steam mixes with the gas. To stop this, tubes were plugged and make it difficult to control temperatures. After plugging, temperatures are: gas 620ºC to 525ºC; steam 225ºC to 370ºC. How we control temperatures within the design limits?
Category: Heat Transfer

Plate heat exchanger design process calculation
I'm looking for a plate heat exchanger design process calculation for a sulfuric acid plant. Can you recommend a good source or provide a solved case as an example?
Category: Heat Transfer

Fluid handling with conventional heat exchangers
What type of problems do you face when handling fibrous fluids in conventional heat exchanger in various industries? What type of heat exchanger is best suitable for this purpose? Please provide design details, applications and advantages compared to conventional types.
Category: Heat Transfer

Finned tube heat transfer equation
I want to design a concentric heat exchanger without a phase change and I want to vary the fins. What is the equation of heat transfer for fin tube?
Category: Heat Transfer

Calculate heat transfer area for a plate-type condenser
We need to distill PoCl₃, which is present in reaction mass. We increase the temperature and distill with 1 tar pressure through a plate-type condenser. For 250 kgs to be distilled with cooling water as utility for condenser jacket, what capacity of plate-type condenser do we need? At what pressure we can pass water through jacket? How do we calculate the heat transfer area? How do we know the thermal conductive?
Category: Heat Transfer

Recycle waste heat
We have waste heat available at 30ºC-40°C in the form of hot water that is thrown to atmosphere via a cooling tower. We want to pump this heat above 100°C. We are also having steam available at 10 kg/cm². A part of the steam is used at 1-5 kg/cm². Can we evaporate the water at 30ºC-40°C and use it above 100°C by means of a thermal vapor recompressor (evaporating water under vacuum and carry away heat by steam ejector)? Can we pump a part of the heat available above 100°C by using the rest of the heat available at 30ºC-40°C?
Category: Heat Transfer

Shear rates for liquid film
What would be the best way to handle cases where apparent viscosities as a function of shear rate may need to be given in the input. How would the shear rates be estimated for the liquid film at the top of the tube and the bottom of the tube? If this can be done, a linear interpolation for the apparent viscosity in each zone could be done. Is there software suitable for the evaporation of Non-Newtonian (pseudoplastic or shear thinning) fluids in the tube side of falling film heat exchangers?
Category: Heat Transfer

Effect of scale in jacketed vessel
What is effect of scale in a vessel jacket on heat transfer? What is amount of heat loss? An example is, what would the heat loss be for a 1-mm scale layer in a vessel jacket, or the same for a 2-mm scale layer?
Category: Heat Transfer

Flow and pressure relation
What may be the reason of pressure or flow drop of steam generated by a boiler when it is taken through a pressure reducing station? What is the relation between flow and pressure?
Category: Heat Transfer

Hot glycol circulation
The ethylene glycol refrigeration system seems to be a bottleneck to production. What characteristics would indicate that the problem is the hydraulic system versus the mechanical refrigeration system? Also how would I determine what incremental benefit I would gain by greater hot glycol circulation, increasing turbulence but lowering the LMDT?
Category: Heat Transfer

Iron content refractory materials
Section 7.3.9 of API standard 560 (revision 3) for Fired Heater for General Refinery Purposes says: "Low iron content (max 1.5%) refractory materials shall be used when total heavy metals content within fuels for burner exceeds 100 ppm." My question: What will happen if I use a refractory having iron more than 1.5% while burning a fuel oil that has 300 ppm heavy metal (Ni+V)?
Category: Heat Transfer

Oil temperature difference
In my unit (an oil system) we regard the temperature of oil after the heater decreases instead of increasing. What is the reason?
Category: Heat Transfer

Reactor content temperature versus oil system temperature
In my unit, which produced formaldehyde from partial oxidation of methanol, we use a reactor (nonadiabtic) for the internal cooling done by thermal oil. The problem is: at startup when we heat the thermal oil, as the temperature of the thermal oil increases, there is a decrease in the temperature. Why is this occurring?
Category: Heat Transfer

Plate heat exchanger fouling factors
How do you calculate the fouling factor in a plate heat exchanger?
Category: Heat Transfer

Redesigning a reflux condensor
How do you design a reflux condensor? The reaction inside the reactor is happening under nitrogen blanketing. In what way can you know how much nitrogen and how much of the product will go to the condensor? In a calculation of a reflux condensor I also saw the term "non-condensable." How can you know how much of the off-gas is non-condensable?
Category: Heat Transfer

Condensor cleaning chemicals
What chemicals are safe and effective to use when cleaning a condensor?
Category: Heat Transfer

Calculating kiln residence time
We have an ilmenite beneficiation plant, in which Fe₂0₃ is reduced to Fe0 in a rotary kiln. I want to know how to calculate residence time in the kiln (as per our ocp of 150 mins) that is 30 m in length.
Category: Heat Transfer

Reducing glycol loss when using TEG
We are using TEG for dehydrating natural gas and one regeneration system for TEG. We are facing problem of glycol loss. How can we reduce that? Reducing flow of stripping gas can help, I think.
Category: Heat Transfer

How a hot-oil system works
Can you explain how a basic hot oil system works? The system includes a hot-oil drum, heater, reboilers and a filter.
Category: Heat Transfer

Rebuilding a graphite block heat exchanger
I'm looking for information on a graphite block heat exchanger. The data plate says "Falls Heat Exchanger Carborundum Kennecott 39-08115, serial number C1405, year 1982," along with some pressure and temperature limits. I have been unable to find anything on-line about this unit, and was wondering if you had any ideas on obtaining info about it. Specifically, I need to disassemble, re-gasket and reassemble it. While this seems straightforward at first, I've gotten myself into a few pickles over the years by not knowing some "trick" or two up front before going in. Any ideas you may have would be greatly appreciated.
Category: Heat Transfer

The effects of elevated nitrite levels
Can you tell me what effect elevated nitrite levels would have on heat transfer system? This system is used to cool oil in turbines. The nitrite levels are in excess of 8,000 ppm.
Category: Heat Transfer

Ice formation on cryogenic piping
I'm writing because ice accumulation on cryogenic piping and equipment is a potential hazard, and we are attempting to quantify the potential thickness that could develop. This information would be helpful in esigning pipe supports, etc. Please comment.
Category: Heat Transfer

What is the right procedure for doing calculations with j-type shell?
If a J-type shell is selected which means divided flow at shell side, can i proceede with calculations by assuming two independent shells on either side of the divider? To elaborate my question a bit more I wish to say that can i divide the mass flow rate by two and can calculate pressure drop and shell side heat transfer coefficient separately for both parts and then later on adding the two sides. What is the right procedure for doing calculations with j-type shell?
Category: Heat Transfer

Determining fouling layer thickness
In sizing a heat exchanger the fouling factor is always indicated and pressure drop is then calculated. Very often the fouling layer thickness is omitted in the calculation, resulting in clean pressure drop rather than required fouled pressure drop. In finding out fouling layer thickness, one will need the fouling layer conductivity (x fouling factor = thickness). The fouling layer conductivity is never specified and is very difficult to estimate. Currently we assume it be the same as the fluid. Is there a method in estimating the fouling layer conductivity by which the layer thickness can be calculated. Assume the fluid properties are known, such as bitumen or water. Fouling is either deposition or scaling.
Category: Heat Transfer

Install a heat transfer fluid spill
We would like to install a Syltherm heat transfer fluid spill detection system to detect any circulating pump leaks. When we had a leak recently at the pump, it generated a lot of vapor and mist delaying the operators to isolate the pump as there was no remore provision to do so. We are planning to install remotely-actuated block valves to isolate pumping system. We are also planning to installa leak detection device at the pump or in the immediate area. Please recommend a device suitable to detect Syltherm heat transfer fluid leaks(vapor and/or liquid)and to transmit the signal to the control room for operators to take remedial actions. This device should be suitable to silicone environment also.
Category: Heat Transfer

Optimum vaporization to circulation ratio
What is the optimum vaporization to circulation ratio in the thermosyphon reboilers with both sides operating under vacuum at the 80C of vaporizing fluid (spent wash in distillery without alcohol) and condensing water vapors? What is the minimum delta T for this case?
Category: Heat Transfer