Issue 4/2004

The author informs about the use of cooling ceilings also for heating the staying spaces of administration buildings. The information is based on requirements of hygienic regulations for keeping the operational temperature which is different from the internal air temperature and which is decisive for reaching the thermal comfort of the stay environment. Further he follows with discussing the limiting parameters, ie. surface temperature of the cooling ceiling – possibility of air humidity condensation, and Fanger’s criterion for the difference of radiation temperatures. The article further describes briefly the types of closed and open cooling ceilings and their use for different types of office rooms. At article conclusion the author indicates different types of hydraulic interconnections of cooling ceilings in combination with heating.

In the article the author informs about the basic principles and technical solution of water loops when designing heating and air conditioning systems of commercial complexes. The system of water loops utilises predominantly low-potential heat from condensers of refrigerating units, arranged in inside spaces of buildings, for heating the peripheral zones when using the heat pumps. The article further indicates the basic components of the system and description of their functions. The conclusion draws attention not only to merits but also to possible difficulties of the proposed system.

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The article informs about results of experiments – heat gains measuring of solar greenhouse built in the loft sloping roof of the boarding house. It continues by this the former work [3] where the results are indicated of the 2D and 3D models. Without indicating the whole greenhouse aperture the heat gains of approx. 45 MJ/d on a clear winter day and of 7 MJ/d under half-clear sky are indicated. Under overcast sky the heat gains are negligible.

The air conditioning of spaces with cooling ceilings is a possible alternative of the environment state conditioning for creating the optimum thermal comfort of persons without high requirements concerning the air distribution. The sensible heat load of the space is carried away by large-surface water-cooled panels which are installed in lower ceilings of the room in most cases. The volumetric air flow of the ventilation equipment operating in parallel may be then reduced to only necessary minimum amount of fresh air. Theoretically the radiant heat transfer between a person and the environment, compared with convection heat transfer, is more advantageous not only from the point of view of thermal comfort creation but also from the point of view of energy consumption (see further). However the systems of cooling ceilings are relatively capital-intensive. The contribution generally deals with advantages and disadvantages of the cooling ceilings use. It pays particular attention to evaluation of the thermal comfort of the space air conditioned in this way, which is documented by a simulation calculation.

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Results acquired by atmosphere investigation of 14 metro stations flooded during floods in 2002 and of 13 non-flooded stations proved neither differences of moulds concentrations in the atmosphere nor differences of further monitored parameters, i.e. relative air humidity and air flow velocity. Twenty months after floods the Prague metro does not constitute a risk for the health of passengers from the point of view of moulds occurrence in the atmosphere.

The article proves by simple balance calculations how difficult is to gain electric power from solar energy by thermodynamic way even in countries with the longest and most intensive insolation. The evaluation is indicated of the utilisation efficiency of the impinging solar energy under the all-day (uninterrupted) solar power station operation, when the night demand of energy is accumulated into siliceous sand during the day.

The author explains the difference between the terms regulation and control. He specifies the principal differences and presents them by examples.