Material Selection and Basics of Spiral Heat Exchanger

Heat exchangers are mechanical components which are used to transfer heat from fluid with high temperature to the fluid with low temperature. This process of heat exchange between the fluids happens due to the phenomena’s called thermal conduction and thermal convection (Bari 2015). Heat exchanger transfer heat by first absorbing the heat from fluid with high temperature through the process of convection, then transferring it to the other side having fluid with low temperature through the process called conduction and then finally transferring it to the fluid with low temperature through the process called convection (Vendat 2000).

Figure 1 working of spiral heat exchanger (Vendat 2000)

Heat exchangers are used in all those applications where heat is needed to be absorbed from the environment or rejected to the environment. Some examples of heat exchangers are domestic water heater which absorb heat from its high temperature surrounding (high temperature of surrounding is due to burning of fossil fuel) and exchange it with the low temperature water (Vendat 2000). Other example of heat exchanger is heat rejected into atmosphere by the vehicle engine where heat exchanger is a fin type heat exchanger which absorb heat of combustion from the engine and deliver it to the surrounding air (Bari 2015).

Figure 2 domestic water heater (Bari 2015)

One of the applications of heat exchanger is the recovery of heat from any industrial or domestic heat source where a lot of heat is being rejected into the environment (Bari 2015). This setup of utilizing the wasted heat is called waste heat recovery system and it is only possible by the use of heat exchanger. Heat exchanger makes use of high temperature fluid coming out of any process as a waste fluid and absorbs its heat (Vendat 2000). Then that particular heat is utilized for any process required for example heating the incoming raw material. As shown in the example below the exhaust coming out of the gas turbine is being utilized by the heat exchanger to heat water convert it into steam. Similar to this the heat exchanger can be utilized in any waster heat recovery system.

Figure 3 waste heat recovery system (Bari 2015)

Heat exchangers are devices used to transfer heat between two mediums of different temperature. There are different types of heat exchangers and their performance depends upon different parameters. Some of the parameters are (Vendat 2000)

Type of flow in spiral heat exchanger

Type of flow include laminar and laminar flow particles moves in a straight line and do not change their position because of which less heat transfer take place. Turbulent flow occurs when Reynolds number exceed above this type of flow every particle of medium flow randomly due to which high heat transfer take place.

Parallel and counter flow spiral heat exchanger

When both fluids flow parallel to each other initially temperature difference is high but as the fluid flow temperature difference decreases due to which lees heat is tranfered.on contrary in counter flow there is greater temperature difference between two mediums because of which more heat is transferred

Material of spiral heat exchanger

Different materials have different thermal conductivity. Higher the thermal conductivity higher will be the heat transfer and vice versa. Spiral heat exchanger consists of two parallel plates folded in spiral shape. Hot fluid enters from the centre and exit at the periphery while cold fluid enters from the periphery and exit from the centre. From one of the study it is concluded that heat transfer rate (HTR) of spiral heat exchanger is more than other type of heat exchanger. More heat transfer take place due to greater contact area (Jamshid Khorshidi 2016)

Material Selection for Spiral Heat Exchanger

In the case of heat exchanger from all the factors involve in heat exchanger design two factors, one the fluid which is being used as a medium in heat exchanger and second the material from which the heat exchanger is manufactured are the most  important of all. Both of these factors decide the working, performance, efficiency and amount of the heat that a heat exchanger can transfer. So the first phase in design of a spiral heat exchanger is the selection of material for the structure of the heat exchanger (Jamshid Khorshidi 2016). Material used in the manufacturing of spiral heat exchanger will define the strength of spiral heat exchanger, thermal conductivity of spiral heat exchanger, eight of spiral heat exchanger and cost of manufacturing of spiral heat exchanger. Selection of material is very critical for the effective working of the heat exchanger so that’s why the proper selection process has to be established for this process. The selection process of the spiral heat exchanger material will consist of number of properties or the requirements which a material should fulfil in order to design an effective spiral heat exchanger.

Following is the list of mechanical properties which material should have in order to get selected (Jamshid Khorshidi 2016)

High conductivity

Material selected for the job should have high conductivity in terms of heat and energy so that maximum heat can be transfer between fluids. The role of material in transfer of heat in spiral heat exchanger is very important. Material absorbed heat from hot fluid using convective heat transfer coefficient between material and fluid. Heat absorbed from fluid is then transfer between two sides of material using conduction and the again between material and fluid using convection. All this mechanism of heat transfer in spiral heat exchanger is depending on the material conductivity. Higher the conductivity of material higher will be the performance and higher will be the heat transfer in spiral heat exchanger for a given temperature difference (Kothandaraman, 2006).


Temperature produce stresses in material which can cause leakage in spiral heat exchanger so material should have good strength. The spiral heat exchanger will be under stress during its operation. This stress can be due to the pressure of the fluid which is moving inside the spiral of the spiral heat exchanger. The stress can also be due to the high temperature of hot fluid, the thermal stresses in material. During heat exchanger the cold fluid will gain heat due to which it can expand inside spiral heat exchanger. This thermal expansion of cold fluid cause stresses in walls of spiral heat exchanger. So the material selected for the manufacturing of spiral heat exchanger should have high strength to resist the stress produce in spiral heat exchanger (Kothandaraman, 2006).


Density of the selected material should be low to keep the weight of the spiral heat exchanger low. Density of material is defined as the mass per unit volume of the material. Greater the density of material from which spiral heat exchanger is manufactured greater will be the mass per unit volume and thus greater will be the weight of the spiral heat exchanger. Material with greater density will be difficult to handle and maintain, so material with the lowest density possible should be selected for the spiral heat exchanger (Kothandaraman, 2006).

Thermal Expansion

Material natural response to heat is the expansion of material in all directions. This expansion of material during heating is called thermal expansion. In spiral heat exchanger the thermal expansion of material can cause distortion in complicated design and can make the entire setup useless. Material with low thermal expansion is recommended for manufacturing of spiral heat exchanger as it will have lower thermal stress which makes it secure and safe to use.

Environmental effect

Material for the manufacturing of spiral heat exchanger should be selected after considering the environmental effect of all shortlisted materials available for the manufacturing of spiral heat exchanger. Material selected for heat exchanger should not affect environment in any aspect which include working, manufacturing and disposal. Material should neither react chemically with the working fluids of spiral heat exchanger nor should it react with the surrounding environment elements of spiral heat exchanger (Kothandaraman, 2006).


Material selected for heat exchanger should be easy to manufacture and can be manufactures using traditional machines. Material should have excellent machinability (material should be easy to machine into required shape of spiral heat exchanger and weldability (material should allow the welding of any required component of spiral heat exchanger). Other than this the material of the spiral heat exchanger should have excelled surface texture and good support for paint jobs.


Material selected for heat exchanger should be a cost effective option in terms of every aspect like material cost, availability, manufacturing cost and disposal cost. Lower material cost means the raw material required for the manufacturing of spiral heat exchanger will be cheap which means less cost of final product. Less manufacturing cost of spiral heat exchanger means less initial investment is required and less final product cost (Kothandaraman, 2006).

Material Mechanical and Thermal Properties

Based on the above discussion on the material mechanical and thermal properties required for the spiral heat exchanger, below is list of mechanical and thermal properties which the selected material for further process of spiral heat exchanger should have (Kothandaraman, 2006).

1.      High Thermal Conductivity

2.      Lower Thermal expansion

3.      High Strength (Yield Strength)

4.      Low Material Density

5.      Machinability

6.      Weldability

7.      Environmental Aspects

8.      Cost

Based on the information obtain from the literature review of different spiral heat exchanger  following are the materials recommended for the manufacturing of the spiral heat exchanger as they all are excelled in the mechanical and thermal properties required for the spiral heat exchanger.

1.      Copper

2.      Aluminum

3.      Cast Iron

4.      Stainless Steel



Aluminum 6061 T6

Cast Iron

Stainless Steel

Conductivity W/mK





Expansion per C * 10^-6





Strength MPa





Density Kg/m^3





















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