# Thermal performances of a “black box” heat exchanger in district heating system

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## Abstract

The procedure for field testing of plate heat exchanger, considered as a black box, is presented in the paper. After the field measurements have been conducted, simple but unambiguous procedure has been used to establish heat performance parameters including the heat duty and fouling factor. Advantage of hereby presented method is that it can be used for analysis of any other similar heat transfer equipment.

## Nomenclature

*a, A, b, B, c*parameters

*c*_{p}specific heat capacities of fluid, [Jkg

^{−1}K^{−1}]*d*_{h}hydraulic diameter, [m]

*k*overall heat transfer coefficient, [Wm

^{−1}K^{−1}]*m*mass flow rate, [kgs

^{−1}]*NTU*number of transfer units, [−]

- Nu
Nusselt number, [−]

*P*heat effectiveness parameter, [−]

- Pr
Prandtl number, [−]

*Q*heat duty, [W]

*R*fouling factor, [m

^{2}KW^{−1}]*R*ratio of heat equivalents, [−]

- Re
Reynolds number, [−]

*R*_{tot}total fouling factor, [m

^{2}KW^{−1}]*S*_{HE}heat exchanger surface area, [m

^{2}]*s*_{Q}deviation of heat duty, [W]

*t*temperature, [°C]

*W*channel width, [m]

*w*velocity, [ms

^{−1}]

## Greek symbols

*α*heat transfer coefficient, [Wm

^{−2}K^{−1}]*δ*distance between plates, [m]

*δ*_{pl}plate thickness, [m]

- Δ
*s*_{Q} dispersion of heat duty, [−]

- Δ
*t*_{av} mean logarithmic temperature difference, [°C]

*λ*thermal conductivity of fluid, [Wm

^{−1}K^{−1})]*λ*_{pl}thermal conductivity of plate, [Wm

^{−1}K^{−1})]*μ*dynamic viscosity, [kg/(m·s)]

*ρ*density, [kgm

^{−3}]

## Indexes

- 1
hot fluid

- 2
cold fluid

*c*correlated

*in*inlet

*m*measured value

*nom*nominal

*out*outlet

## Notes

### Acknowledgments

The research work is funded by Ministry of Education, Science and Technological Development of Republic of Serbia.

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