Abstract
Experiments have been carried out in order to investigate the stabilization of water temperature with a water-PCM heat exchanger. The water-PCM heat exchanger was of a rather simple design. It was a round tube, through which the water flowed, surrounded with an annular layer of PCM. The heat exchanger was divided into one meter long segments (modules) and the water temperature was monitored at the outlet of each of the segments. A paraffin-based PCM with the melting temperature of 42 °C was used in the experiments. The experimental set-up consisted of two water reservoirs kept at different temperatures, the water-PCM heat exchanger, PC controlled valves and a data acquisition system. As the first step a response to a step change in the water temperature at the inlet of the heat exchanger was investigated. Subsequently, a series of experiments with a square wave change of temperature at the inlet of the exchanger were carried out. The square wave temperature profile was achieved by periodic switching between the two water reservoirs. Several amplitudes and periods of temperature square wave were used. The results of experiments show that a water-PCM heat exchanger can effectively be used to stabilize the flowing water temperature when the inlet temperature changes are around the melting range of the PCM.
Highlights
A constant fluid temperature plays an important role in many applications from laboratory experiments to the extracorporeal blood circulation
The behaviour of sensible heat storage used for this purpose is rather independent of the fluid temperature
Under quasi-stationary conditions, that when the fluid temperature at the inlet of the attenuator follows one of the waveforms the heat flows from the fluid to the thermal storage material during the first half of the period and it flows from the heat storage material to the fluid during the second half of the period
Summary
A constant fluid temperature plays an important role in many applications from laboratory experiments to the extracorporeal blood circulation. The temperature fluctuations can be either stochastic or they can follow a certain pattern (e.g. depending on a dead band of a temperature controller) Thermal storage with both sensible and latent heat storage materials can be employed to attenuate the fluid temperature fluctuations. Klimes and Charvat [6] presented a heuristic approach used in optimal design of the fluid temperature attenuator with a PCM They developed a numerical model of the attenuator with the use of the control volume method and the effective heat capacity approach [7]. Numerical investigation of the influence of the inlet temperature wave forms on the thermal behaviour of the attenuator with sensible and latent heat storage materials is reported in [9]
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