Issue 4/1998

The paper reviews all kinds of ventilation used in prefabricated houses including the systems, which exist but have not been applied in this country. Guide costs for the reconstruction of ventilation in a dwelling unit are given at price level of 1997. Possibilities of reconstruction and modernisation of dwelling venti/ation are presented with examples of different types of prefabricated flats.

The paper presents a risk study concerning the back-penetration of fungal spores from polluted filters into the environment. The risk is evaluated for XY combined air cleaner and humidifier according to the mode of filter pollution.

The paper compiles information about copper in drinking water. Its concentration is higher in water piping made from copper. Health risks and insufficient legislation in this area are pointed out.

The paper deals with physical fields, which can be biologically hazardous in the living and working environment. Possible field effects are presented and information about the Czech and European standards is given in this context.

The paper deals with the influence of outdoor and indoor air pollution on people's health. Individual physical, chemical and biological pollutants as well as their combinations are discussed in the context of their short-term and long-term negative impact on respiratory organs.

The tightness of metal-sheet air ducts has an influence on their function and operating costs. The paper reviews the sources of duct leakage, measurement procedures and tightness classification according to national and foreign standards. A calculation method based on investment and operating costs is presented for the optimum leakage determination.

A comment on objections raising in the context of a horizontal single-pipe heating system.

The paper treats of the radiator local control with focus on thermostatic radiator valves with linear and equal percentage characteristics.

The paper presents successful application of two-stage heat pump in a food factory. Ammonia is used as a coolant. The first stage of heat pump consist of screw compressors while the second is fitted with high-pressure reciprocating compressor. Maximum of available heat is used for pre-heating of service water. The results are compared with the operation of a single-stage cooling device with no recovery of heat energy. It has been proved that the heat pump operation is more environmentlly friendly and the investment in this device will return quickly (in 3.1 years).

The paper deals with heat and mass transfer in impact flow striking perpendiculariy a horizontal surface formed by water level or by a wet fabric material. Experimental study was performed to estimate the influence of the jet velocity, distance between the nozzle and the surface, surface area, and nozzle geometry. Heat and mass transfer calculation was determined from the measurement results and Iiterature review. A new instrument was designed on the basis of the experimental results to measure the humidity of air, poliuted air, also at high temperatures, using the impact f10w technique. A schematic drawing of the instrument is presented. The paper compares theoretical and experimental data representing the relationship between humidity ratio, water tempe¬rature in immersed tank, and air temperature.

The paper compares two types of indoor climate analysis of an industrial hall. The first is based on mathematical modelling in Excel spreadsheet processor, which is very useful for design practice. The second one was experimental, based on data measured under normal operating conditions. The experimental results proved the accuracy of computer simulation. 80th types of analysis are focused on dynamic performance and interaction between ventilating system and building construction of the hall.