Heat exchanger, double-pipe

The correlation for forced convective heat transfer in conduits (equation 12.10) can be used to predict the heat transfer coefficient in the annulus, using the appropriate equivalent diameter  

Some designs of double-pipe exchanger use inner tubes fitted with longitudinal fins. 

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Reaction times can be as short as 10 minutes in a continuous flow reactor (1). In a typical batch cycle, the slurry is heated to the reaction temperature and held for up to 24 hours, although hold times can be less than an hour for many processes. After reaction is complete, the material is cooled, either by batch cooling or by pumping the product slurry through a double-pipe heat exchanger. Once the temperature is reduced below approximately 100°C, the slurry can be released through a pressure letdown system to ambient pressure. The product is then recovered by filtration (qv). A series of wash steps may be required to remove any salts that are formed as by-products. The clean filter cake is then dried in a tray or tunnel dryer or reslurried with water and spray dried. 

Double-Pipe Scrapea-Surface Crystallizer This type of equipment consists of a double-pipe heat exchanger with an internal agitator fitted with spring-loaded scrapers that wipe the wall of the inner pipe. The cooling hquid passes between the pipes, this annulus being dimensioned to permit reasonable shell-side velocities. The scrapers prevent the buildup of solids and maintain a good film coefficient of heat transfer. The equipment can be operated in a continuous or in a recirculating batch manner. 

For flow parallel to tubes or in an annular space, e.g. a double-pipe heat exchanger, use... 

One of the simplest and cheapest types of heat exchanger is the concentric pipe arrangement known as the double-pipe heat exchanger. Such equipment can be made up from standard fittings and is useful where only a small heal transfer area is required. Several units can be connected in series to extend the capacity. ... 

The whole set-up for partial oxidation comprises a micro mixer for safe handling of explosive mixtures downstream (flame-arrestor effect), a micro heat exchanger for pre-heating reactant gases, the pressure vessel with the monolith reactor, a double-pipe heat exchanger for product gas cooling and a pneumatic pressure control valve to allow operation at elevated pressure [3]. 

Figure 6.4a, b. Gasketed plate and frame and double pipe heat exchangers, Time base mid-2004... 

The bulk of the styrene is to be heated to 85°C before being charged. This is done in a vertical double-pipe heat exchanger, which is directly above the reactor. To prevent polymerization from occurring in the heat exchanger or piping system, there are to be no obstructions between this heat exchanger and the reactors. 

Heat is to be transferred from one process stream to another by means of a double pipe heat exchanger. The hot fluid flows in a 1 in. sch 40 tube, which is inside (concentric with) a 2 in. sch 40 tube, with the cold fluid flowing in the annulus between the tubes. If both fluids are to flow at a velocity of 8 ft/s and the total equivalent length of the tubes is 1300 ft, what pump power is required to circulate the colder fluid Properties at average temperature p = 55 lbm/ft3, p = 8 cP. 

A. Zavala-Rio, R. Femat, and G. Solis-Perales. Countercurrent double-pipe heat exchangers are a special type of positive systems. In First Multidisciplinary International Symposium on Positive Systems Theory and Applications (POSTA 2003), volume IEEE LNCIS 294, pages 385-392, Roma, Italy, August 2003. 

Flow of Two Fluids. The major applications are in absorption, extraction, and distillation, with and without reaction. Other applications, also quite important, are for shell-and-tube or double-pipe heat exchangers, and noncatalytic fluid-solid reactors (blast furnace and ore-reduction processes). 

The simplest form of a heat exchanger consists of two concentric cylindrical tubes, the double pipe heat exchanger, as schematically represented in Figure 8 ... 

Figure 8 Schematic representation of a double pipe heat exchanger...

Double-pipe heat exchangers are widely used for smaller flow rates. When the heat-transfer coefficient outside is too low, a solution consists of using longitudinal finned tubes as an extended surface. 

Fig. 10-2 Double-pipe heat exchange (a) schematic (b) thermal-resistance network for overall heat transfer...

Consider the double-pipe heat exchanger shown in Fig. 10-2. The fluids may flow in either parallel flow or counterflow, and the temperature profiles for these two cases are indicated in Fig. 10-7. We propose to calculate the heat transfer in this double-pipe arrangement with... 

Water at the rate of 68 kg/min is heated from 35 to 75°C by an oil having a specific heat of 1.9 kJ/kg °C. The fluids are used in a counterflow double-pipe heat exchanger, and the oil enters the exchanger at 110°C and leaves at 75°C. The overall heat-transfer coefficient is 320 W/m2 °C. Calculate the heat-exchanger area. 

Instead of the double-pipe heat exchanger of Example 10-4, it is desired to use a shell-and-tube exchanger with the water making one shell pass and the oil making two tube passes. Calculate the area required for this exchanger, assuming that the overall heat-transfer coefficient remains at 320 W/m2 °C. 

Hot water at 90°C flows on the inside of a 2.5-cm-ID steel tube with 0.8-mm wall thickness at a velocity of 4 m/s. This tube forms the inside of a double-pipe heat exchanger. The outer pipe has a 3.75-cm ID, and engine oil at 20°C flows in the annular space at a velocity of 7 m/s. Calculate the overall heat-transfer coefficient for this arrangement. The tube length is 6.0 m. 

A small steam condenser is designed to condense 0.76 kg/min of steam at 83 kPa with cooling water at 10°C. The exit water temperature is not to exceed 57°C. The overall heat-transfer coefficient is 3400 W/m2 °C. Calculate the area required for a double-pipe heat exchanger. 

A counterflow double-pipe heat exchanger is used to heat water from 20 to 40°C by cooling an oil from 90 to 55°C. The exchanger is designed for a total heat transfer of 29 kW with an overall heat-transfer coefficient of 340 W/m2 °C. Calculate the surface area of the exchanger. 

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