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“ Not only do these air conditioning systems use a lot of power , they are also loud and create drafts . They can also cause hygiene problems if they are not properly maintained ,” explains the researcher .
SIMULATIONS To determine whether heat pumps can be combined with radiators or under-floor heating systems for use as a cooling system , the researcher and her team conducted initial tests under laboratory conditions in the climate chamber with radiators and under-floor heating systems .
Digital twins of the heating systems were then tested using the building simulation software WUFI ® Plus to determine whether the laboratory measurements matched the software calculations . “ We can use the digital twins to produce a valid representation of reality and calculate the effect of the overall system in a wide range of application scenarios . This allows us to identify the specific areas where heat pumps plus radiators or under-floor heaters are most effective .”
The simulation software creates a ( hygric ) link between heat and humidity in the calculation . The simulations can be scaled to any type of building , taking into account a range of parameters such as room and window size , the size of the heating elements , the external temperature and the design and number of windows .
The researchers can examine other parameters , such as energy requirements and comfort . This allows for a comprehensive evaluation of heating and cooling systems . The tests found that both radiators and under-floor heating systems have the potential to reduce the ambient air temperature in the summer significantly and to produce a pleasant cooling effect in office spaces with a standard size of 16m ², windows of up to 3m ² and two workers , without unwanted condensation forming on cold surfaces .
The inflow temperature of the system must be regulated depending on the dew point of the ambient temperature to avoid structural damage from condensation . “ The dew point temperature is a critical figure that we need to consider in our calculations . This is because moisture condenses on a surface when the surface is colder than the dew point temperature of the air . Therefore , it is important to consider the dew point temperature when cooling . In other words , if the dew point temperature is 13 degrees Celsius , the water we feed through the heating system cannot be any colder than that , otherwise
View of the corner of the test room with radiator .
the water from the air will condense on the heating element and supply lines , causing damp .”
UP TO 65 % REDUCTION IN OVER TEMPERATURE DEGREE HOURS Another important criterion for the calculations is over temperature degree hours . This unit of measurement refers to the number of hours and Kelvins above the limit temperature of the room , which is 26 degrees Celsius , in the year .
A maximum of 1200 over temperature degree hours per year are permitted in residential buildings , and just 500 in offices . The researchers ’ calculations showed a reduction of over 40 % in over temperature degree hours for radiators measuring 70 cm by 1 m . For radiators twice that size , a 65 % reduction can be achieved compared to an uncooled room .
“ All in all , we demonstrated that the cooling performance achieved using radiators is sufficient with a moderate window surface area share . However , a higher window surface area share requires a larger cooling area to achieve comfortable indoor climate conditions . This area can be provided using underfloor heating systems , which also produce a significantly greater cooling effect , as our tests have shown ,” says Giglmeier in summary .
Heat pumps with cooling functions could be an alternative to expensive cooling systems in existing buildings . The extent to which the overall system affects the user ’ s comfort – for example , whether floors become too cold , or temperature changes affect floor coverings and other materials in the room – remains to be investigated .
The assessment of potential conducted by the IBP researchers was sponsored by the Fraunhofer High- Performance Centre Mass Personalisation . RACA
© Fraunhofer IBP
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