Helical Heat Exchanger CFD Simulation by ANSYS Fluent

Description

Introduction

A heat exchanger is a system used to transfer heat between two or more fluids. Heat exchangers are used in both cooling and heating processes. The fluids may be separated by a solid wall to prevent mixing or they may be in direct contact. They are widely used in space heating, refrigeration, air conditioning, power stations, chemical plants, petrochemical plants, petroleum refineries, natural-gas processing, and sewage treatment. The classic example of a heat exchanger is found in an internal combustion engine in which a circulating fluid known as engine coolant flows through radiator coils and air flows past the coils, which cools the coolant and heats the incoming air. Another example is the heat sink, which is a passive heat exchanger that transfers the heat generated by an electronic or a mechanical device to a fluid medium, often air or a liquid coolant.

Helical Heat Exchanger Project description

In this project, the heat transfer inside a helical heat exchanger is investigated. The helical heat exchanger consists of a number of coils (helical tubes) with a helix curve (similar to a spring) that are embedded in a shell. To increase the heat transfer level, several pipes are placed in a spiral format next to each other and all are connected to one inlet and outlet. Numerous experimental studies have been performed on the flow and heat transfer characteristics inside helical tubes. Energy equation is activated to obtain temperature distribution inside computational domain. standard k-epsilon model is exploited to solve turbulent flow equations. It should be noted that the ideal gas model has been used to determine the density changes in proportion to temperature.

Helical Heat Exchanger Geometry & Mesh

The geometry of this project is designed in CATIA and meshed in GAMBIT. The mesh type used for this geometry is unstructured and the element number is 890710.

CFD simulation settings

The key assumptions considered in this project are:

• Simulation uses a pressure-based solver.
• The present simulation and its results are steady and do not change as a function time.
• We ignore the effect of gravity.

The applied settings are summarized in the following table.

	Models
Viscous model		k-epsilon
	k-epsilon model	standard
	near wall treatment	standard wall function
Energy		on
	Boundary conditions
Inlet		Velocity inlet
	Inlet2	5 m/s
	Temperature	340 K
	Inlet-2	5m/s
	Temperature	300 K
Outlet		Pressure outlet
	Gauge pressure	0 Pa
Walls		Stationary wall
wall	Heat flux	0 W/m2
wall.5	Thermal condition	coupled
	Solution Methods
Pressure-velocity coupling		coupled
Spatial discretization	Pressure	PRESTO!
	Momentum	first order upwind
	Energy	first order upwind
	turbulent kinetic energy	first order upwind
	turbulent dissipation rate	first order upwind
	Initialization
Initialization method		Standard
	gauge pressure	0 Pa
	Velocity (x,y,z)	(0,0,0) m/s
	temperature	334.3642K
	Turbulent kinetic energy	0.09375 m2/s2
	Turbulent dissipation rate	78.72302 m2/s3

Results

We obtain and present the contours of velocity, temperature, etc. in both 3D and 2D.

All files, including Geometry, Mesh, Case & Data, are available in Simulation File. By the way, Training File presents how to solve the problem and extract all desired results.