Which heat exchanger is most efficient

High heat-transfer coefficient and high turbulence due to even flow distribution are important. However, a plate heat exchanger regenerator is restricted to low viscosities. With high viscosities, a special tubular may be required.

Spiral type can be used for liquids of not-too-high viscosity because of good flow distribution, when the flow is turbulent in the two single passages. Pressure drop must be sufficiently high to yield a velocity to create turbulence. Reynolds number should be greater than 1, Heat-Sensitive Liquids e. Plate exchangers fulfill these requirements best.

Spiral type and special tubular styles have the longest hold-up times. Strict temperature control is essential. Wall temperature and fouling considerations may be very important with heat sensitive or corrosive liquids. Vapor Condensation e. If extensive and frequent manual cleaning is necessary, a plate exchanger, possibly a box condenser, may be utilized.

Shell and tube condenser is applicable if carbon steel can be used throughout, or at least for the shell. Cooling Water e. High-Temperature Application e. Also, shell and tube and spiral exchangers are suitable. High Viscosity, Fouling or Crystallizing e. This website requires certain cookies to work and uses other cookies to help you have the best experience.

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This Website Uses Cookies By closing this message or continuing to use our site, you agree to our cookie policy. Learn More This website requires certain cookies to work and uses other cookies to help you have the best experience. Home » Finding the Best Heat Exchanger. October 26, Order Reprints. You might think that all heat exchangers are the same, but guess again. There are several different types and models, each of which is designed for its own specific function and use.

Why heat exchangers? The correct answer to this question is, of course, the need for thermal processing of various products, be they within the food, dairy, chemical or pharmaceutical industries. Heat excahnger price varies by style. Report Abusive Comment Thank you for helping us to improve our forums. Fluid types include: Water Oils Milk Cosmetics Pharmaceuticals Thermal properties of fluids include: Temperature Acidity Flow rate Corrosiveness Viscosity Plate heat exchangers handle low-to medium-viscosity fluids at higher flow rates than tube or scraped-surface models.

Manufacturers of heat exchangers typically ask for additional particulars about fluids before they can provide an accurate cost quotation, including: Heat load Temperature program Physical properties of liquids in question if not a standard product such as milk, water, or beer, for example Desired working pressure Maximum permitted pressure drop Available steam pressure.

Consider phasing Heat exchangers fall into two basic categories based on the fluids liquids or gases being processed. Single-phase heat exchangers process only one phase--liquid or gas Two-phase heat exchangers can be used to boil liquid into a gas.

Such units are sometimes called boilers. They can also be used in condensing and evaporation applications. Units configured to cool gases so they condense into a liquid are called condensers. Key design factors of heat exchangers Some heat exchanger designs achieve higher heat-transfer rates and operate at higher temperatures than other designs.

Considerations when selecting a heat exchanger The table below outlines several considerations to weigh when selecting a heat exchanger. When to choose a Plate-and-frame heat exchanger In this section, we compare shell-and-tube with plate-and-frame heat exchangers based on: Energy use Footprint Ease of maintenance Capacity adjustment Capital expense.

Smaller footprint and greater scalability make plate heat exchangers the best choice in applications where space is limited or scale flexibility is required. Energy use Plate heat exchangers are up to five times more efficient than shell-and-tube designs. Footprint Shell-and-tube heat exchangers require more floor space than plate heat exchangers, as the comparison on the left illustrates. Ease of maintenance High-quality plate-and-frame heat exchangers can operate efficiently for many years without maintenance.

Capacity adjustment Plate heat exchangers make capacity adjustment relatively easy. Capital expense Cost of ownership is always a critical factor in the decision-making process. When to choose a shell-and-tube heat exchanger The basic shell-and-tube principle moves product through a bundle of parallel tubes with heating fluid between and around the tubes.

The reason is cost: high-pressure tubes are less expensive than high-pressure shells. The fouling issue comes down to the impact of fouling on exchanger performance and how easily you can clean the equipment. Fouling in heat exchangers occurs for several reasons: Crystallization: This is caused by salts that dissolve and crystalize upon cooling. Consider shell-and-tube designs for fluids with high salt content subject to high-temperature changes.

Sedimentation, or deposits of sand, rust, or other compounds: Sedimentation comes from corrosion products, metal oxides, silt, alumina, and diatomic organisms microalgae and their excrement. Velocity adjustments can be made in some cases to reduce the impact of sedimentation. Corrosion: Fouling due to corrosion can affect the heat-transfer performance of equipment, so consider the properties of heat exchanger materials and fluids to avoid corrosion when possible.

Incrustation: the accumulation of a crust or coating of processed fluids, minerals, or cleaning agents on the surface of heat exchanger parts.

Scaling: a type of incrustation caused by calcium carbonate, calcium sulfate, and silicates. Biological growth: Sources of biological fouling include bacteria, nematodes, and protozoa. When to choose a scraped-surface heat exchanger Some processes require heat transfer that prevents fouling from viscous and sticky products.

Making Your Selection To help with the model-selection process, manufacturers typically provide comparison charts like the one below.

Guide to Choosing the Right Heat Exchanger This guide is designed for processors, production managers, and mechanical engineers to help in the heat exchanger selection process.

Next Steps With various heat exchanger designs on the market, selecting the most suitable design for transferring heat between fluids can be difficult!

To learn how we can help, contact us today! Contact Us. Fouling in Heat Exchangers. March 30th, Fouling in Heat Exchangers Fouling is the formation of unwanted material deposits on heat transfer surfaces during process heating and cooling.

The log mean temperature for a heat exchanger is calculated using the following equation. Heat transfer in a heat exchanger is by conduction and convection. The rate of heat transfer, "Q", in a heat exchanger is calculated using the following equation. Consider the following example of a heat exchanger operated under identical conditions as a counter flow and then a parallel flow heat exchanger.

Inserting the above values into heat transfer Equation for the counter flow heat exchanger yields the following result. Inserting the above values into the heat transfer Equation for parallel flow heat exchanger yields the following result. The results demonstrate that given the same operating conditions, operating the same heat exchanger in a counter flow manner will result in a greater heat transfer rate than operating in parallel flow.

In actuality, most large heat exchangers are not purely parallel flow, counter flow, or cross flow; they are usually a combination of the two or all three types of heat exchangers.

This is due to the fact that actual heat exchangers are more complex than the simple components shown in the idealized figures used to depict each type of heat exchanger. The reason for the combination of the various types is to maximize the efficiency of the heat exchanger within the restrictions placed on the design.

That is, size, cost, weight, required efficiency, type of fluids, operating pressures, and temperatures, all help determine the complexity of a specific heat exchanger. One method that combines the characteristics of two or more heat exchangers and improves the performance of a heat exchanger is to have the two fluids pass each other several times within a single heat exchanger.