Design and Operation of a Shell and Tube Heat Exchanger (Single Phase Flow)

CHAPTER ONE

INTRODUCTION

Shell and tube heat exchangers are used extensively throughout the process industry and as such a basic understanding of their design, construction and performance is important to the practicing engineer.

The objective of this paper is to provide a concise review of the key issues involved in their thermal design without having to refer to the extensive literature available on this topic.

The optimum thermal design of a shell and tube heat exchanger involves the consideration of many interacting design parameters which can be summarized as follows:

Process

  • Process fluid assignments to shell side or tube side.
  • Selection of stream temperature specifications.
  • Setting shell side and tube side pressure drop design limits.
  • Setting shell side and tube side velocity limits.
  • Selection of heat transfer models and fouling coefficients for shell side and tube side.

Mechanical

  • Selection of heat exchanger TEMA layout and number of passes.
  • Specification of tube parameters – size, layout, pitch and material.
  • Setting upper and lower design limits on tube length.
  • Specification of shell side parameters materials, baffle cut, baffle spacing and clearances.
  • Setting upper and lower design limits on shell diameter, baffle cut and baffle spacing.

There are several software design and rating packages available, including A spen BJAC, HTFS and CC-THERM, which enable the designer to study the effects of the many interacting design parameters and achieve an optimum thermal design. These packages are supported by extensive component physical property databases and thermodynamic models.

It must be stressed that software convergence and optimization routines will not necessarily achieve a practical and economic design without the designer forcing parameters in an intuitive way. It is recommended that the design be checked by running the model in the rating mode.

Detailed mechanical design and construction involving tube sheet layouts, thicknesses, clearances, tube supports and thermal expansion are not considered but the thermal design must be consistent with the practical requirements.

1.2. STATEMENT OF THE PROBLEM

Products of crude oil are used in different application areas especially in industries (textile industry) but from their ordinary properties the amount of energy transferred becomes un sufficient to the required process and also the final out put product gained from the process is also quality-less.

1.3. OBJECTIVES

1.3.1. GENERAL OBJECTIVES

The general objective of this paper is to know and understand design of shell and tube heat exchanger. Hence design of shell and tube heat exchanger for single phase flow manually and using C++ programing is the general objective.

1.3.2. SPECIFIC OBJECTIVES

Based on the general objective the specific objective is considering specific activities that build up to the general objective. Due to this the specific objective of this paper is to know and practice the kern method (log min temperature difference method LMTD and effectiveness method NTU) and to develop software programing capabilities (Borland C++).