4-way water-outlet shelled heat exchanger

Contents

INTRODUCTION

THERMAL DESIGN CALCULATION OF RECUPERATOR

Determination of thermodynamic and thermophysical parameters of heat carriers

2. Determination of mass flow rate of coolant

3. Determination of average temperature head

Calculation of Reynolds number in tube space of heat exchanger

Calculation of the Nusselt number in the tube space of the heat exchanger

6. Determination of heat transfer coefficient to heated heat carrier

Calculation of Reynolds number in annulus of heat exchanger

Calculation of the Nusselt number in the annulus of the heat exchanger

9. Determination of heat transfer coefficient to heated heat carrier

Opredeleniye Highway of coefficient of a heat transfer

We determine the calculated heat exchange surface area

Recalculate the speed and Reynolds criterion for heating and heated heat carriers

If the selected heat exchanger is multi-pass, the average temperature difference is specified

Structural calculation of heat exchanger

HYDRAULIC CALCULATION OF HEAT EXCHANGER

Determination of hydraulic friction resistance

Determination of thermal insulation thickness of the apparatus

CONCLUSION

Literature

Introduction

Heat exchangers, or heat exchangers, are devices for transferring heat from some media (hot heat carriers) to others (cold heat carriers). Heat exchangers are used for heating and cooling substances in various aggregate states, evaporation of liquids and condensation of vapors, distillation and sublimation, absorption and adsorption, melting of solids and crystallization, removal and supply of heat during exo and endothermic reactions, etc. Accordingly, heat exchangers are referred to as preheaters, coolers, evaporators, condensers, distillers, sublimators, melters, etc.

Heat exchangers according to the heat transfer method are divided into surface ones, where there is no direct contact of heat carriers, and heat transfer occurs through a solid wall, and mixing ones where heat carriers contact directly. Surface heat exchangers, in turn, are divided into recuperative and regenerative, depending on the simultaneous or alternating contact of the heat carriers with the wall separating them. Surface type heat exchangers are also classified by purpose (heaters, refrigerators, etc.); in the mutual direction of heat carriers (direct flow, countercurrent, mixed current, etc.); by heat exchange surface material; by number of moves, etc.

Most the kozhukhotrubny heat exchangers used for heat exchange between streams in various aggregate states became widespread (steam - liquid, a zhidkostzhidkost, gas - gas, gas - liquid). The apparatus consists of a bundle of pipes placed inside a cylindrical body (shell), welded from sheet steel, less often cast. The tubes are embedded in or welded to two tube grates depending on the properties of the structural materials. Tubes are placed in a bundle in staggered order, along the vertices of an equilateral triangle, with a pitch of s/d = (1.25-2.20), where d is the outer diameter of the tubes. Device is equipped with two detachable covers with unions for inlet and outlet of heat carrier moving inside pipes. Tube and tube spaces are separated. Second heat carrier moves in annular space equipped with inlet and outlet unions. As a rule, the flow that contains suspended solids (for convenience of cleaning) moves through the pipes, is under high pressure (in order not to weigh the body) or has aggressive properties (to protect the body from corrosion). The flow area of the annular space is much larger (sometimes 2 times) than the total live section of the pipes, therefore, with the same volumetric flow rates of heat carriers, the heat transfer coefficient from the annular space is lower. To eliminate this phenomenon, the heat carrier speed is increased by placing various partitions in the tube space. In shell and tube heat exchangers, sufficiently large ratios of heat exchange surface to volume and mass are achieved. The dimensions of the heat exchange surface can be easily varied within wide limits, the design has sufficient strength and withstands normal loads during assembly, transportation and installation of the heat exchanger, as well as internal and external stresses under normal operating conditions. Cleaning the shell and tube heat exchanger is difficult, and its components, most susceptible to corrosion, - gaskets and pipes - can be easily replaced. Design features allow use of this type in almost all cases, including extremely low or high temperatures and pressures, large temperature gradients, during evaporation and condensation and the use of highly contaminated and corrosive heat carriers.

An important element of most shell and tube heat exchangers is a set of partitions. They protect the pipes from bending and vibration, and also direct flow across the pipes to improve heat transfer (and, as a result, increase the pressure drop).

Shell and tube heat exchangers can be used as heat exchangers, coolers, condensers and evaporators.

The shell and tube apparatus are arranged vertically or horizontally according to local conditions; if it is necessary to extend the coolant path, they can be connected in series, and if it is impossible to place the required number of pipes in one case, they are connected in parallel, they can be one-, two-, four- and six-way along the pipe space. The pipes, casing and other structural elements may be made of carbon or stainless steel.

The design distinguishes between heat exchangers with fixed tube grids, in which both grids are rigidly fixed to the body and the pipes cannot be freely elongated, and heat exchangers with compensating devices, in which the pipes can be freely elongated.

In heat exchangers with fixed pipe grids with different thermal elongation of pipes and casing, temperature stresses occur; therefore, such heat exchangers are used with a small temperature difference between the pipes and the casing.

Conclusion

In the course design, a shell-tube water-water heat exchanger was calculated. As a result of the calculation, the main sizes of the apparatus were determined: the diameter of the body, the number, diameter and lengths of the tubes in the casing; speed of coolant movement.

Dimensions of the selected heat exchanger: casing diameter D = 600 mm, internal diameter of pipes inside the casing d = 25 mm, total number of pipes in the apparatus 206 with a length of 6 m each.

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