Estimation of Nusselt number and effectiveness of double‐pipe heat exchanger with Al2O3–, CuO–, TiO2–, and ZnO–water based nanofluids

The rate of heat transfer in helical pipes is much more than straight pipes. In the present study, heat transfer and fluid flow in a double‐coil heat exchanger with an innovative swirl generator with a curved structure in the inner channel (hot side) are studied, numerically. The proposed turbulator has a curved structure and 12 blades to produce swirl flows. Also, two holes are considered at the semi‐conical part of the turbulator. The effects of geometrical parameters of the proposed turbulator including the inner radius of the turbulator and the radius of the turbulator's holes are evaluated. Results indicate that the maximum effectiveness belongs to the case with inner diameter of the turbulator and radius of turbulator' holes equal to 19 and 3.6 mm, respectively, at ṁ=0.008 normalknormalgnormal/normals. Also, the generated swirl flows by the turbulator has a significant influence on heat transfer augmentation. Furthermore, a high inner radius of the turbulator leads to an increase in heat transfer rate and effectiveness, consequently. As a result, by increasing the inner radius of turbulator by 26.7%, the effectiveness rises by 80% (maximum at trueṁ = 0.008 kg/s). Increasing the radius of turbulator's hole by 133.34% leads to an growth in effectiveness of about 50% (maximum at trueṁ = 0.058 kg/s).

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Influence of a curved conical turbulator on heat transfer augmentation in a helical double‐pipe heat exchanger

Ajarostaghi

2020

“…2,3 Many researchers 4,5 have presented an analytical method for multiple streams, one-dimensional HX to determine temperature distribution for all the fluids with an assumption that no multiple eigenvalues exist in the solution. The variety of configurations of a two-fluid HX available are tube-intube HX [6][7][8] and tube with a helical coil 9 ; and for a three-fluid HX, the two basic configurations are tube-in-tube HX 10 and tube-in-tube with a helical coil carrying the third fluid. 11 The researchers [12][13][14][15] presented an explicit/iterative solution for directional dependence for the class of three-fluid HX.…”

Section: Introductionmentioning

confidence: 99%

Joule–Thomson effect investigations on a cryogenic three‐fluid–three thermal communication heat exchanger

Chodankar¹,

Aswatha

Krishna

et al. 2021

The present study investigates the Joule-Thomson (JT) effect due to pressure drop on three-fluid heat exchangers (HXs) with three thermal communications. The increased miniaturization of cryogenic HXs has led to the introduction of the JT effect. The present study investigates JT effects on a three-fluid HX with three communications presenting different JT effects, which leads to a rise or drop in effectiveness values. The study is carried out using finite element analysis and MATLAB, considering seven nondimensional parameters of which one is JT pressure drop. The highest effectiveness is achieved for the positive JT effect at the hot stream. This improved effectiveness at hot fluid is achieved by maintaining the size (number of transfer units) of the HX more than 3.1, along with the ratio of the cold fluid heat capacity to the hot fluid heat capacity above 0.8 and the intermediate fluid temperature above 0.7.

“…In passive methods, however, no external input power is required, But, the drawback with these methods, is the drops in the pressure associated with the introduced enhancement technique 3 . Interesting examples are additives for the working fluids, 4 coiled tubes, flow turbulators, pipe insertions, and, of course, fins.…”

Section: Introductionmentioning

confidence: 99%

Experimental investigation of heat transfer enhancement in a double pipe heat exchanger with a twisted inner pipe

Ali

Jalal

2021

In the present work, an experimental investigation is conducted to address the influence of inner pipe twisting on the overall performance of a double pipe heat exchanger. With the fluid to fluid heat exchange, both parallel and counter flow directions are examined as well. In addition to the original elliptical pipe, three pipes with different numbers of twisting (3, 5, and 7 twists per unit length) constructed from the elliptical pipe are considered where the heat transfer rate and pressure drop are addressed. All tests are carried out in the turbulent flow regime where the Reynolds number (Re) ranging from 5000 to 26,000 and water is used as the working medium. The obtained outcomes show that for both flow directions, there is an enhancement in the heat exchanger overall performance with all considered twisting pipes. The maximum enhancement in the Nusselt number is found to be 1.8 for the parallel flow and around 2.2 for the counter flow compared with the original pipe. The inner pipe with 7 twists, however, improves the overall performance the most, where a maximum performance enhancement factor of 1.63 and 1.9 are observed at Reynolds number of 26,000 in the parallel and counter flow configurations, respectively.