**Greek symbols**

general, the heat exchanger effectiveness is affected by the baffle arrangement and type. It is found that helical baffle is preferable than double segmental baffle which yields 15% higher effectiveness. Larger baffle separation distance consistently shows a significantly decreasing heat transfer rate as indicated by lower ΔT. This in turn lowers the heat exchanger effectiveness quite substantially. In addition, angle also quite essential to optimize. For the utilization of helical baffle, only changing 5°

The utilization of nanofluid has been demonstrated to enhance the heat transfer process yielding higher effectiveness. Even at the extremely low concentration of nanoparticles, *i.e.*, 0.002 to 0.025%, the water-ethylene glycol based nanofluids containing SiO2@TiO2 core-shell nanoparticles enable enhancement of heat

exchanger effectiveness by 20%. This finding is essential as it is not necessary to use high concentration of nanoparticles to improve heat exchanger effectiveness while avoiding fouling inside the tubing system of shell and tube heat exchanger. Another set of examples has been shown that using water based working fluid using Al2O3. Increasing volume fraction of Al2O3 nanoparticles significantly boosts the effectiveness up to 0.422 which is plausibly a result of increasing thermal conductivity of

Financial support by the Center of Research and Development (*Lembaga Penelitian dan Pengabdian Kepada Masyarakat*) of Universitas Negeri Surabaya and the directorate of research and community development (*Direktorat Riset dan Pengabdian Kepada Masyarakat*) of Institut Teknologi Sepuluh Nopember is highly acknowledged. Authors also would like to thank to the Mechanical Engineering Department and Heat Transfer Laboratory of Universitas Negeri Surabaya for their

C

C

Authors declare that there is no conflict of interest.

Cc, Ch Heat capacity of hot and cold fluid, W/o

Cp,h, Cp,c Specific heat of hot and cold fluid, J/kg <sup>o</sup>

C

C or K

*m*\_ *<sup>h</sup>*, *m*\_ *<sup>c</sup>* mass flow rate, kg/s

*qmax* Maximum heat transfer (W) *qactual* Actual heat transfer (W)

*u* Velocity of the medium, m/sec.

*ε* heat exchanger effectiveness, n.d

h, c Refers to hot and cold fluid i, o Refers to inflows and outflows

*h* Enthalpy, J/kg <sup>o</sup>

*T* Temperature, <sup>o</sup>

*V* Volume, m<sup>3</sup>

to 7° already lowers the effectiveness from 0.50 down to 0.32.

*Heat Transfer - Design, Experimentation and Applications*

the water base fluid.

**Acknowledgements**

technical support.

**Nomenclature**

**Subscripts**

**208**

**Conflict of interest**

