# Thermal Performance of a New Coiled Tube Heat Exchanger
> Experimental study on figure-eight helical coil heat exchangers, exploring the impact of hot water inlet temperature and flow rate on heat transfer efficiency.

Tags: heat-exchanger, mechanical-engineering, thermodynamics, thermal-performance, helical-coil, fluid-dynamics, energy-efficiency
## Introduction
- Definition of heat exchanger as a thermal energy transfer device.
- Introduction of Shell & Helical Pipe Heat Exchangers (HTHE).
- Objective: Investigation of a novel infinity-shaped coiled circular pipe for improved heat transfer.

## Literature Review
- Summary of research on double-shell passes and spiral corrugation.
- Discussion of nanofluids (Al₂O₃/water) in helical pipes.
- Comparison between helical coils and straight pipes regarding secondary flow formation.

## Theoretical Calculations
- Formulas for Heat Transfer Rate ($Q$), Nusselt Number ($Nu$), Reynolds Number ($Re$), and LMTD.
- Assumptions: Steady state, counter-flow, no phase change, no internal heat generation.

## Experimental Apparatus & Procedure
- Novel ∞-coil design with 3,950 mm length.
- Test rig details: 50L hot water tank (3,000W heater), K-type thermocouples, and LUTRON temperature logger.
- Test matrix: Reynolds numbers between 8,000 – 13,000; hot water temperatures 40–70°C.

## Results & Discussion
- **Nusselt Number:** Increases with inlet temperature; max $Nu \approx 250$ at 70°C.
- **Heat Transfer Coefficient:** Increases by 70% when moving from 40°C to 70°C (up to 12,000 W/m²K).
- **Heat Transfer Rate:** Increases 10%–40% with higher temperature differentials.
- **Flow Regime:** Reynolds numbers (8,000–13,000) confirm fully turbulent flow.

## Conclusions
- The figure-eight (∞) coil induces centrifugal secondary flow and enhances turbulence.
- Higher temperatures reduce viscosity, further increasing $Re$ and enhancement mechanisms.
- The design significantly outperforms traditional single-loop configurations.
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