Heat exchangers are widely used in industry both for cooling and heating large scale industrial processes. The type and size of heat exchanger used can be tailored to suit a process depending on the type of fluid, its phase, temperature, density, viscosity, pressures, chemical composition and various other thermodynamic properties. Fin fan air cooled heat exchanger Texas City Texas
In many industrial processes there is waste of energy or a heat stream that is being exhausted, heat exchangers can be used to recover this heat and put it to use by heating a different stream in the process. This practice saves a lot of money in industry, as the heat supplied to other streams from the heat exchangers would otherwise come from an external source that is more expensive and more harmful to the environment. Fin fan air cooled heat exchanger Texas City Texas
Heat exchangers are used in many industries, including:
In waste water treatment, heat exchangers play a vital role in maintaining optimal temperatures within anaerobic digesters to promote the growth of microbes that remove pollutants. Common types of heat exchangers used in this application are the double pipe heat exchanger as well as the plate and frame heat exchanger. Finn fan air cooled heat exchanger Texas City Texas
In aircraft Finn fan air cooled heat exchanger Texas City Texas
In commercial aircraft heat exchangers are used to take heat from the engine’s oil system to heat cold fuel. This improves fuel efficiency, as well as reduces the possibility of water entrapped in the fuel freezing in components. Fin fan air cooled heat exchanger Texas City Texas
Current market and forecast Finn fan air cooled heat exchanger Texas City Texas
Estimated at US$42.7 billion in 2012, the global demand of heat exchangers will experience robust growth of about 7.8% annually over the next years. The market value is expected to reach US$57.9 billion by 2016 and to approach US$78.16 billion by 2020. Tubular heat exchangers and plate heat exchangers are still the most widely applied product types. Fin fan air cooled heat exchanger Texas City Texas
model of a simple heat exchanger Finn fan air cooled heat exchanger Texas City Texas
A simple heat exchange might be thought of as two straight pipes with fluid flow, which are thermally connected. Let the pipes be of equal length L, carrying fluids with heat capacity {\displaystyle C_{i}} (energy per unit mass per unit change in temperature) and let the mass flow rate of the fluids through the pipes, both in the same direction, be {\displaystyle j_{i}} (mass per unit time), where the subscript iapplies to pipe 1 or pipe 2. Finn fan air cooled heat exchanger Texas City Texas
Temperature profiles for the pipes are {\displaystyle T_{1}(x)} and {\displaystyle T_{2}(x)} where x is the distance along the pipe. Assume a steady state, so that the temperature profiles are not functions of time. Assume also that the only transfer of heat from a small volume of fluid in one pipe is to the fluid element in the other pipe at the same position, i.e., there is no transfer of heat along a pipe due to temperature differences in that pipe. By Newton’s law of cooling the rate of change in energy of a small volume of fluid is proportional to the difference in temperatures between it and the corresponding element in the other pipe:
{\displaystyle {\frac {du_{1}}{dt}}=\gamma (T_{2}-T_{1})}
{\displaystyle {\frac {du_{2}}{dt}}=\gamma (T_{1}-T_{2})}
( this is for parallel flow in the same direction and opposite temperature gradients, but for counter-flow heat exchange countercurrent exchange the sign is Finn fan air cooled heat exchanger Texas City Texas opposite in the second equation in front of {\displaystyle \gamma (T_{1}-T_{2})} ) Finn fan air cooled heat exchanger Texas City Texas
, where {\displaystyle u_{i}(x)} is the thermal energy per unit length and γ is the thermal connection constant per unit length between the two pipes. This change in internal energy results in a change in the temperature of the fluid element. The time rate of change for the fluid element carried along by the flow is: Fin fan air cooled heat exchanger Texas City Texas
{\displaystyle {\frac {du_{1}}{dt}}=J_{1}{\frac {dT_{1}}{dx}}}
{\displaystyle {\frac {du_{2}}{dt}}=J_{2}{\frac {dT_{2}}{dx}}}
where {\displaystyle J_{i}={C_{i}}{j_{i}}} the “thermal mass flow rate”. The differential equations governing the heat exchanger may now written as: Finn fan air cooled heat exchanger Texas City Texas
{\displaystyle J_{1}{\frac {\partial T_{1}}{\partial x}}=\gamma (T_{2}-T_{1})}
{\displaystyle J_{2}{\frac {\partial T_{2}}{\partial x}}=\gamma (T_{1}-T_{2}).}
Note that, since the system is in a steady state, there are no partial derivatives of temperature with respect to time, and since there is no heat transfer along the pipe, there are no second derivatives in x as is found in the heat equation. These two coupled first-order differential equations may be solved to yield:
{\displaystyle T_{1}=A-{\frac {Bk_{1}}{k}}\,e^{-kx}}
{\displaystyle T_{2}=A+{\frac {Bk_{2}}{k}}\,e^{-kx}}
where {\displaystyle k_{1}=\gamma /J_{1}}, {\displaystyle k_{2}=\gamma /J_{2}},
{\displaystyle k=k_{1}+k_{2}}
(this is for parallel-flow, but for counter-flow the sign in front of {\displaystyle k_{2}} is negative, so that if {\displaystyle k_{2}=k_{1}}, for the same “thermal mass flow rate” in both opposite directions, the gradient of temperature is constant and the temperatures linear in position x with a constant difference {\displaystyle (T_{2}-T_{1})} along the exchanger, explaining why the counter current design countercurrent exchange is the most efficient ) Fin fan air cooled heat exchanger Texas City Texas
and A and B are two as yet undetermined constants of integration. Let {\displaystyle T_{10}} and {\displaystyle T_{20}} be the temperatures at x=0 and let {\displaystyle T_{1L}}and {\displaystyle T_{2L}} be the temperatures at the end of the pipe at x=L. Define the average temperatures in each pipe as:
Using the solutions above, these temperatures are:
By the conservation of energy, the sum of the two energies is zero. The Finn fan air cooled heat exchanger Texas City Texas quantity {\displaystyle {\overline {T}}_{2}-{\overline {T}}_{1}} known as the Log mean temperature difference, and a measure of the effectiveness of the heat exchanger in transferring heat energy. Fin fan air cooled heat exchanger Texas City Texas
Construction. Finn fan air cooled heat exchanger Texas City Texas
The distance between the sheets in the spiral channels maintained by using spacer studs that were welded prior to rolling. Once the main spiral pack has rolled, alternate top and bottom edges welded and each end closed by a gasketed flat or conical cover bolted to the body. This ensures no mixing of the two fluids occurs. Any leakage from the periphery cover to the atmosphere, or to a passage that contains the same fluid. . Finn fan air cooled heat exchanger Texas City Texas
Self cleaning[. Finn fan air cooled heat exchanger Texas City Texas
Spiral heat exchangers are often used in the heating of fluids that contain solids and thus tend to foul the inside of the heat exchanger. The low pressure drop lets the SHE handle fouling more easily. The SHE uses a “self cleaning” mechanism, whereby fouled surfaces cause a localized increase in fluid velocity, thus increasing the drag (or fluid friction) on the fouled surface, thus helping to dislodge the blockage and keep the heat exchanger clean. “The internal walls that make up the heat transfer surface often rather thick, which makes the SHE very robust, and able to last a long time in demanding environments.” They also easily cleaned, opening out like an oven where any buildup of foulant can removed by pressure washing. . Finn fan air cooled heat exchanger Texas City Texas
Self-cleaning water filters used to keep the system clean and running without the need to shut down or replace cartridges and bags. . Finn fan air cooled heat exchanger Texas City Texas
Flow arrangements. Finn fan air cooled heat exchanger Texas City Texas
A comparison between the operations and effects of a cocurrent and a countercurrent flow exchange system depicted by the upper and lower diagrams respectively. In both it assumed (and indicated) that red has a higher value (e.g. of temperature) than blue and that the property being transported in the channels therefore flows from red to blue. Note that channels contiguous if effective exchange to occur (i.e. there can no gap between the channels). . Finn fan air cooled heat exchanger Texas City Texas
There are three main types of flows in a spiral heat exchanger:
Counter-current Flow: Fluids flow in opposite directions. These used for liquid-liquid, condensing and gas cooling applications. Units usually mounted vertically when condensing vapour and mounted horizontally when handling high concentrations of solids. . Finn fan air cooled heat exchanger Texas City Texas
Spiral Flow/Cross Flow: One fluid in spiral flow and the other in a cross flow. Spiral flow passages welded at each side for this type of spiral heat exchanger. This type of flow suitable for handling low density gas, which passes through the cross flow, avoiding pressure loss. It can used for liquid-liquid applications if one liquid has a considerably greater flow rate than the other. . Finn fan air cooled heat exchanger Texas City Texas
Distributed Vapour/Spiral flow: This design that of a condenser, and usually mounted vertically. It designed to cater for the sub-cooling of both condensate and non-condensables. The coolant moves in a spiral and leaves via the top. Hot gases that enter leave as condensate via the bottom outlet. . Finn fan air cooled heat exchanger Texas City Texas
Applications. Finn fan air cooled heat exchanger Texas City Texas
The Spiral heat exchanger is good for applications such as pasteurization, digester heating, heat recovery, pre-heating (see: recuperator), and effluent cooling. For sludge treatment, SHEs are generally smaller than other types of heat exchangers. These used to transfer the heat.
Selection. Finn fan air cooled heat exchanger Texas City Texas
Due to the many variables involved, selecting optimal heat exchangers is challenging. Hand calculations possible, but many iterations typically needed. As such, heat exchangers most often selected via computer programs, either by system designers, who typically engineers, or by equipment vendors. . Finn fan air cooled heat exchanger Texas City Texas
To select an appropriate heat exchanger, the system designers (or equipment vendors) would firstly consider the design limitations for each heat exchanger type. Though cost is often the primary criterion, several other selection criteria are important:
High/lowpressure limits. Finn fan air cooled heat exchanger Texas City Texas
Thermal performance. Finn fan air cooled heat exchanger Texas City Texas
Temperature ranges. Finn fan air cooled heat exchanger Texas City Texas
Product mix (liquid/liquid, particulates or high-solids liquid) . Finn fan air cooled heat exchanger Texas City Texas
Pressure drops across the exchanger
Fluid flow capacity
Cleanability, maintenance and repair. Finn fan air cooled heat exchanger Texas City Texas
Materials required for construction. Finn fan air cooled heat exchanger Texas City Texas
Ability and ease of future expansion. Finn fan air cooled heat exchanger Texas City Texas
Material selection, such as copper, aluminum, carbon steel, stainless steel, nickel alloys, ceramic, polymer, and titanium. . Finn fan air cooled heat exchanger Texas City Texas
Small-diameter coil technologies are becoming more popular in modern air conditioning and refrigeration systems because they have better rates of heat transfer than conventional sized condenser and evaporator coils with round copper tubes and aluminum or copper fin that have been the standard in the HVAC industry. Small diameter coils can withstand the higher pressures required by the new generation of environmentally friendlier refrigerants. Two small diameter coil technologies are currently available for air conditioning and refrigeration products: copper microgroove and brazed aluminum microchannel. . Finn fan air cooled heat exchanger Texas City Texas
Choosing the right heat exchanger (HX) requires some knowledge of the different heat exchanger types, as well as the environment where the unit must operate. Typically in the manufacturing industry, several differing types of heat exchangers used for just one process or system to derive the final product. For example, a kettle HX for pre-heating, a double pipe HX for the ‘carrier’ fluid and a plate and frame HX for final cooling. With sufficient knowledge of heat exchanger types and operating requirements, an appropriate selection can made to optimise the process. . Finn fan air cooled heat exchanger Texas City Texas. Finn fan air cooled heat exchanger Texas City Texas
Nueva Orleans• Baton Rouge• Shreveport• Lafayette• Lake Charles• Kenner• Bossier City• Monroe• Alexandria• Houma• NuevaIberia• Slidell• Ruston• Sulphur• Hammond• Natchitoches• Gretna• Chalmette• Opelousas• Zachary• Thibodaux• Pineville• Baker• Crowley• Minden• West Monroe• MorganCity• Abbeville• Bogalusa• Mandeville• Bastrop• DeRidder• Eunice• Jennings• Denham Springs• Gonzales• Harahan • Houston• SanAntonio• Dallas• Austin• Fort Worth• El Paso• Arlington• Corpus Christi• Plano• Laredo• Lubbock• Garland• Irving• Amarillo• GrandPrairie• Brownsville• Pasadena• Mesquite• McKinney• McAllen• Killeen• Waco• Carrollton•Beaumont• Abilene• Frisco• Denton• Midland• Wichita Falls• Odessa• Round Rock• Richardson• Tyler• Lewisville• College Station• SanAngelo• Pearland• Texas City Texas