Natural gas is transported from producing regions to consumption regions by using transmission pipelines at high pressures. At consumption regions

the pressure of natural gas is reduced in city gate stations (CGSs). Before the pressure reduction process

the temperature of natural gas is increased usually by using a water bath heater

which burns natural gas as fuel

to protect against freezing of natural gas. These types of heat exchangers have a low efficiency and consume a lot of fuel to generate the required heat. In the current study

the twisted configuration of the heating coil is proposed and investigated to enhance the heat transfer through a water bath heater with a nominal capacity of 1000 m

3

·h

-1

. Firstly

the implementation procedure is validated with data collected from the CGS of Qaleh-Jiq (located in Golestan province of Iran). A very good agreement is achieved between the obtained results and the real data. Then

three different twist ratios are considered to examine the twisting effects. The proposed technique is evaluated in the terms of velocity

temperature

and pressure variations

and the results are compared with the conve

ntional case

i.e

. straight configuration. It is found that both the heat transfer rate and the pressure drop augment as the twist ratio is raised. Finally

it is concluded that the twisted tubes can reduce the length of the gas coil by about 12.5% for the model with low twist ratio

18.75% for the model with medium twist ratio

and 25% for the model with high twist ratio as compared to the straight configuration.