21-04-2012, 03:11 PM
Model of a Heat pipe heat exchanger
Model of a heat pipe heat exchanger.pdf (Size: 164.75 KB / Downloads: 174)
GENERAL DESCRIPTION OF COMPONENT
According to one manufacturer (IV Produkter) a heat pipe heat exchanger, figure 1, function
as follows:
“ The heat exchanger is built of internally surface extended pipes filled by tetrafluoretan 134a.
The pipes are expanded into aluminium lamellas. An air tight wall probhites leakage between
the air streams. The exhaust air flows through the lower part of the exchanger and the cold
outdoor air through the upper part. The tetrafluoretan evaporates in the lower part and rises to
the upper part where it condenses and flows back to the lower part by gravity.”
Implementation in EES
The model is implemented in EES as a module in the format developed within “Annex 40”.
Available / Necessary Data
To customize the model, manufacturers’ data is preferable, but the model may be customized
using measured data. By using manufacturers data or measured data different aspects of the
coil recovery loop may be studied. Manufacturers’ data may be taken from datasheets or from
dimensioning software provided by the supplier.
Implementation of FPT
The model is implemented in a handheld tool for functional performance test of a air handling
unit (Eriksson 2003) where the heat pipe is connected to other models for simulation of an air
handling unit as a whole. The tool is under development and no valid test results currently
exist.
Calibration of model
An air handling unit from the Swedish manufacturer ”IV Produkter” has been tested in the lab
of the Swedish National Testing and Research Institute (SP). One of the components in the air
handling unit is a heat pipe heat exchanger. The model has been calibrated against data from
the laboratory test. The parameters of the model that are used for
calibration are the tube configuration
parameter, number of tube rows, area of condenser and evaporator (Sc, Sh), heat
transfer resistance in tube on condenser side (Rhpc), a constant part of heat transfer (Ac, Ah)
and the constant part of the evaporator tube heat resistance (Ai_h). The calibration is performed
using the built in optimization algorithm of EES and the result is shown in the figure
below.