The fins on the air side of the cooler can also be crimped for a rough finish, increasing air turbulence and improving the rate of heat transfer to the air. Regardless of liquid-to-air cooler construction, any design will more rapidly remove heat with the addition of convection.
Adding a fan to a cooler increases cooling exponentially. Cooling fans can be any size, from tiny dc fans used in the computer industry, to high horsepower ac motors used in industrial applications. Extreme duty mobile applications using dc fans can pull upwards of 40 A, which is the upper range of reasonable usage for 12 V applications, and is taxing on the electrical system in the best of cases.
When mobile applications are severe, the fan motor can be hydraulic. With hydraulic energy, the fan can be high power while using absolutely no electrical current. Although some electric coolers can remove over hp worth of heat, they can block a commercial doorway because of their unwieldy size.
Liquid-to-liquid coolers use water or coolant to remove heat from the hydraulic fluid. Water transfers heat orders of magnitude more efficiently than air, and the same wall of air coolers could be matched in performance by a shell and tube cooler the size of a small bazooka. The problem, of course, is liquid-to-liquid heat exchangers require water or coolant to do their job.
If you have unlimited supply of fresh water, you can simply use that water to continuously run through your cooler or control its flow thermostatically. Tap water can also be used for cooling, although it can be expensive using the municipal water supply.
In large plants or factories, a centralized cooling system can be put in place to supply coolant to the various machines of the plant. This is the most environmentally friendly option, but requires expensive infrastructure, such as complex plumbing and large chiller units exterior to the building. The product flows by the inner tubes while the service does it by the external channel. In general terms, the main uses of a tubular heat exchanger are as follows:. The tubular design in heat exchangers represents one of the most traditionally used configurations, due to its good operation and versatility.
The main advantages of tubular heat exchangers are as follow:. The tubular heat exchanger is a process equipment used in different industries, and its applications are very diverse and varied. The advantages of tubular heat exchangers make them very robust, reliable and low maintenance equipment, due to the absence of joints. Heat Exchangers Technical Documentation. Este sitio web utiliza cookies para que usted tenga la mejor experiencia de usuario.
What is a tubular heat exchanger? Design of a tubular heat exchanger. A key factor for the design of heat exchangers is to characterize the behaviour of the product in an accurate way, through laboratory tests, where we determine and analyze the main properties of the product : Density. Specific heat. Thermal conductivity. Basic components of a tubular heat exchanger.
The basic components of a tubular heat exchanger are as follow: Tube bundle :The tube bundle is the set of tubes that provide the heat transfer surface between the fluid that circulates inside the tubes and the fluid that circulates through the shell. In this set of tubes is where the product to be heated is located. Tube sheet : The tube sheet is a metal plate that has been perforated or drilled, and where the tubes that form the tubular heat exchanger are housed, which are fixed by expansion or welding.
In the event that extra leak protection is required, a double tubular sheet DTS can be used. Baffles : The main objective of the baffles is to control the general direction of flow on the side of the housing. For example, in water-to-water heat transfer applications, the warmer water loses heat which is then transferred to the cooler water and neither change to a gas or solid.
On the other hand, in two-phase heat exchangers , fluids do experience a phase change during the heat transfer process. The phase change can occur in either or both of the fluids involved resulting in a change from a liquid to a gas or a gas to a liquid. Typically, devices that employ a two-phase heat transfer mechanism require more complex design considerations than ones that employ a single-phase heat transfer mechanism.
Some of the types of two-phase heat exchangers available include boilers, condensers, and evaporators. Based on the design characteristics indicated above, there are several different variants of heat exchangers available.
Some of the more common variants employed throughout industry include:. The most common type of heat exchangers, shell and tube heat exchangers are constructed of a single tube or series of parallel tubes i.
Other design characteristics available for this type of heat exchanger include finned tubes , single- or two-phase heat transfer, countercurrent flow, cocurrent flow, or crossflow arrangements, and single, two, or multiple pass configurations. Some of the types of shell and tube heat exchangers available include helical coil heat exchangers and double pipe heat exchangers, and some of the applications include preheating , oil cooling , and steam generation.
A form of shell and tube heat exchanger, double pipe heat exchangers employ the simplest heat exchanger design and configuration which consists of two or more concentric, cylindrical pipes or tubes one larger tube and one or more smaller tubes.
As per the design of the shell and tube heat exchanger, one fluid flows through the smaller tube s , and the other fluid flows around the smaller tube s within the larger tube. The design requirements of double pipe heat exchangers include characteristics from the recuperative and indirect contact types mentioned previously as the fluids remain separated and flow through their own channels throughout the heat transfer process.
However, there is some flexibility in the design of double pipe heat exchangers, as they can be designed with cocurrent or countercurrent flow arrangements and to be used modularly in series, parallel, or series-parallel configurations within a system. For example, Figure 4, below, depicts the transfer of heat within an isolated double pipe heat exchanger with a cocurrent flow configuration.
Also referred to as plate type heat exchangers , plate heat exchangers are constructed of several thin, corrugated plates bundled together. Each pair of plates creates a channel through which one fluid can flow, and the pairs are stacked and attached—via bolting, brazing, or welding—such that a second passage is created between pairs through which the other fluid can flow. The standard plate design is also available with some variations, such as in plate fin or pillow plate heat exchangers.
Plate fin exchangers employ fins or spacers between plates and allow for multiple flow configurations and more than two fluid streams to pass through the device.
Pillow plate exchangers apply pressure to the plates to increase the heat transfer efficiency across the surface of the plate.
Some of the other types available include plate and frame , plate and shell , and spiral plate heat exchangers. Boilers, condensers, and evaporators are heat exchangers which employ a two-phase heat transfer mechanism.
As mentioned previously, in two-phase heat exchangers one or more fluids undergo a phase change during the heat transfer process, either changing from a liquid to a gas or a gas to a liquid. Condensers are heat exchanging devices that take heated gas or vapor and cool it to the point of condensation, changing the gas or vapor into a liquid.
On the other hand, in evaporators and boilers , the heat transfer process changes the fluids from liquid form to gas or vapor form.
Heat exchangers are employed in a variety of applications across a wide range of industries. Consequently, there are several variants of heat exchangers available, each suitable for the requirements and specifications of a particular application.
Beyond the variants mentioned above, other types available include air cooled heat exchangers , fan cooled heat exchangers , and adiabatic wheel heat exchangers. While there are a wide variety of heat exchangers available, the suitability of each type and its design in transferring heat between fluids is dependent on the specifications and requirements of the application.
Those factors largely determine the optimal design of the desired heat exchanger and influence the corresponding rating and sizing calculations. Some of the factors that industry professionals should keep in mind when designing and choosing a heat exchanger include:.
The specific type of fluids—e. For example, if corrosive, high temperature, or high pressure fluids are involved, the heat exchanger design must be able to withstand the high stress conditions throughout the heating or cooling process.
Image credit: CG Thermal. Another method is by choosing a design suited for the fluid properties: plate heat exchangers are capable of handling low to medium pressure fluids but at higher flow rates than other types of heat exchangers, and two-phase heat exchangers are necessary when handling fluids which require a phase change throughout the heat transfer process.
Other fluid and fluid stream properties that industry professionals may keep in mind when choosing a heat exchanger include fluid viscosity, fouling characteristics, particulate matter content, and presence of water-soluble compounds.
The thermal output of a heat exchanger refers to the amount of heat transferred between fluids and the corresponding temperature change at the end of the heat transfer process.
The transference of heat within the heat exchanger leads to a change of temperature in both fluids, lowering the temperature of one fluid as heat is removed and raising the temperature of the other fluid as heat is added. The desired thermal output and rate of heat transfer help determine the optimal type and design of heat exchanger as some heat exchanger designs offer greater heater transfer rates and can handle higher temperatures than other designs, albeit at a higher cost.
After choosing the optimal type and design of a heat exchanger, a common mistake is purchasing one that is too big for the given physical space. Oftentimes, it is more prudent to purchase a heat exchanging device in a size that leaves room for further expansion or addition, rather than choosing one which fully encompasses the space.
For applications with limited space, such as in airplanes or automobiles, compact heat exchangers offer high heat transfer efficiencies in smaller, more lightweight solutions. Characterized by high heat transfer surface area to volume ratios, several variants of these heat exchanging devices are available, including compact plate heat exchangers. While it is necessary to choose a heat exchanger which effectively fulfills the requirements of the applications, it is also important to keep in mind the overall costs of the chosen heat exchanger to better determine whether the device is worth the investment.
For example, an initially expensive, but more durable heat exchanger may result in lower maintenance costs and, consequently, less overall spend over the courses of a few years, while a cheaper heat exchanger may be initially less expensive, but require several repairs and replacements within the same period of time.
Designing the optimal heat exchanger for a given application with particular specifications and requirements as indicated above involves determining the temperature change of the fluids, the heat transfer coefficient, and the construction of the heat exchanger and relating them to the rate of heat transfer.
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