heat exchanger

The large heat loss from Passive-stack ventilation (PSV) systems quite often makes natural ventilation systems unattractive and it is therefore desirable to implement heat recovery in PSV stacks. As the stackpressure is usually about a few Pascal, it is crucial that the heat recoveryunit used in a PSV system produces even lower pressure loss, which is extremely difficult to achieve with the conventional plate heat exchangers. This work is concerned with an a low pressure-loss heat recovery device based on heat pipes.

It is demonstrated how Modelica™ is used in an application to develop models that are useful when solving real problems. Modelica is a new unified modeling language being developed in an international effort to promote object-oriented and non-causal modelling, and exchange of model libraries. The application is a heat exchanger where1 the media are liquids, typically water. This type of heat exchangers can be used for district heating of houses and for production of hot tap water. The model developed illustrates very nicely the power of Modelica.

The paper deals with simulation of the heat exchanger and model evaluation. There are presented partial differential equations of heat exchanger model, which assume liquid mediums. Presented, in the paper, model is used as an approximation for three different type heat exchangers. The purpose of these investigations was to explain weather the same model could match well to different of shape and type exchangers by adjusting some model parameters. There is shown a method of determining model parameters. Results of simulation are compared with measured data.

A new parametrical model for the prediction of the thermal performance of the earth to air heat exchangers is presen1ed. The system consists of an earth tube, buried in the ground, through which ambient or indoor air is propelled and cooled by the bulk temperature of the natural ground. The proposed model has been developed by analysing temperature data of the circulated air at the pipe's outlet using a systematic parametrical process.