Double-pipe heat exchangers are devices that provide the transfer of thermal energy between two fluids at different temperatures. The major use of these heat exchangers is the sensible heating or cooling process of fluids where small heat transfer areas are required. The oil cooler is an example of these processes. In this study, fouled finned, clean finned, fouled unfinned, and clean unfinned double-pipe heat exchangers used as an oil cooler in ships have been compared. In thermal design, suggested different Nusselt number equations have been used, and the results of these equations have been shown in tables and figures. As a result, it is evaluated that using fouled finned double-pipe heat exchanger as oil cooler in ships is the most appropriate selection.
1. Introduction
A double-pipe heat transfer exchanger consists of one or more pipes placed concentrically inside another pipe of a larger diameter with appropriate fittings to direct the flow from one section to the next. One fluid flows through the inner pipe (tube side), and the other flows through the annular space (annulus). The inner pipe is connected by U-shaped return bends enclosed in a return-bend housing. A typical double-pipe heat transfer exchanger is shown in Fig. 1. Double-pipe heat exchangers can be arranged in various series and parallel arrangements to meet pressure drop. The major use of the double-pipe heat exchanger is the sensible heating or cooling process of fluids where small heat transfer areas (up to 50 m2) are required. This configuration is also very suitable for one or both of the fluids at high pressure because of the smaller diameter of the pipes. The major disadvantage is that they are bulky and expensive per unit of heat transfer surface area.
These double-pipe heat exchangers are also called hairpin heat exchangers, and they can be used when one stream is a gas, viscous liquid, or small in volume. These heat exchangers can be used under severe fouling conditions because of the ease of cleaning and maintenance. The outer surface of the inner tube can be finned, and then, the tube can be placed concentrically inside a large pipe, as shown in Fig. 2. In another type, there are multi tubes, finned or bare, inside a larger pipe. The fins increase the heat transfer surface per unit length and reduce the size and, therefore, the number of hairpins required for a given heat duty. Integrally, resistance-welded longitudinal fins have proven to be the most efficient for double-pipe heat exchangers. Fins are most efficient when the film coefficient is low.
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FAQs
A double-pipe heat transfer exchanger consists of one or more pipes placed concentrically inside another pipe of a larger diameter with appropriate fittings to direct the flow from one section to the next. One fluid flows through the inner pipe (tube side), and the other flows through the annular space (annulus).
What type of heat exchanger is an oil cooler? ›
There are three main types of heat exchangers: shell and tube, fin and tube, and fin and fin. Shell and tube heat exchangers are most commonly used in liquid-cooled oil coolers. They are made up of a series of tubes that run through the cooler housing.
What are the advantages of double pipe heat exchanger? ›
The use of double pipe heat exchangers significantly enhances energy efficiency in industrial processes. These heat exchangers are designed to transfer heat between two process fluids efficiently, maximizing heat transfer rates while monitoring mass flow rates.
What is the performance of a double pipe heat exchanger? ›
The coefficient of convective heat transfer increased numerically as the volume concentration and Reynolds number increased. The heat transfer coefficient and thermal conductivity rise by 20% and 4.7%, respectively, at a volume concentration of 5%.
What is the principle of double pipe heat exchanger? ›
A double pipe heat exchanger is a type of heat exchanger that works by using two pipes to carry out its work. This unit is commonly used for transporting air and heat. The goal of a heat exchanger is to allow two separate flows to interact at a conductive barrier, which can allow thermal energy transfer.
What is the 2 3 rule for heat exchanger design? ›
The “two-thirds rule” from API RP 521 (API, 2008) states: For relatively low-pressure equipment, complete tube failure is not a viable contingency when the design pressure of the low-pressure side is equal to or greater than two-thirds the design pressure of the high-pressure side.
What are the two types of oil coolers? ›
Engine oil coolers are generally broken into two types: oil-to-water and oil-to-air. An oil-to-water cooler passes the engine oil through a heat exchanger element of some sort that enables the engine's coolant to either add heat to cold oil or to pull heat from excessively hot oil.
What is the best oil for heat exchanger? ›
Mineral oil is used as a heat transfer medium for a variety of applications. Compared to some of the synthetic fluids available, it offers better thermal stability at high temperatures, easier maintenance and disposal requirements, and a smaller environmental impact. It also generally comes at a lower price point.
What is the best type of oil cooler? ›
Folded (bent) oil coolers are the most affordable and at the same time provide an ideal level of cooling. Their advantage is simple installation and a number of dimensions from which you can choose, whether it concerns the size itself or the outputs.
What are the limitations of double pipe heat exchangers? ›
The disadvantage of the double-pipe heat exchanger is that it covers a large area. At the same time, the metal consumption per unit heat transfer area is much, about 5 times that of the shell-and-tube heat exchanger. There are many pipe joints, which are easy to leak and large flow resistance.
Researchers have investigated the use of nanofluids - fluids containing nanoparticles that boost thermal characteristics - to improve the performance of heat exchangers. The use of nanofluids can improve the efficiency of double-pipe heat exchangers.
What is a double pipe heat exchanger used to cool? ›
Question: A double-pipe heat exchanger is used to cool a hot fluid before it flows into a system of pipes. The inner surface of the pipes is primarily coated with polypropylene lining. The maximum use temperature for polypropylene lining is 107°C (ASME Code for Process Piping, ASME B31.
What is the process design of a double pipe heat exchanger? ›
The basic structure of a double pipe heat exchanger consists of two concentric tubes (Figure 1) and is usually commercialized in a hairpin structure (Figure 2). If the thermal service demands a higher heat transfer area, several hairpins can be interconnected.
What is the temperature range of double pipe heat exchanger? ›
They have a limited temperature range and are not normally used above 250°C. As described in Chapter 4, the potential range of application of double-pipe heat exchangers is wide.
What is another name for a double pipe heat exchanger? ›
This type of heat exchanger is known as hairpin, jacketed pipe, jacketed u-tube, and pipe in pipe exchanger. They can contain one pipe or pipe bundle (less than 30), and the outer pipe must have a diameter of less than 200mm.
What is thermal design of heat exchanger? ›
Thermal design of a shell and tube heat exchanger typically includes the determination of heat transfer area, number of tubes, tube length and diameter, tube layout, number of shell and tube passes, type of heat exchanger (fixed tube sheet, removable tube bundle etc), tube pitch, number of baffles, its type and size, ...
What is the inlet temperature in the double pipe heat exchanger? ›
In a double-pipe heat exchanger, the cold fluid is water with an inlet temperature 20°C and mass flow rate 20 kg/s and the hot fluid water inlet temperature 80°C and mass flow rate 10 kg/s.
What is the correction factor for a double pipe heat exchanger? ›
Both the 1-1 shell-and-tube heat exchanger and the double-pipe heat exchanger have the same heat-exchanger correction factor, FT= 1. This is because in both cases the hot side and the cold side encounter each other only in one sense, either co-currently or counter-currently.
