Title of Contribution to ROOMVENT 2004

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sheet. The sheet is heated and then radiates to thewooden floorboard and the people’s feet that areplaced beneath the kneeler pad.Figure 1. Heating elements applied in the pew2.1 Seat heating elementBack heatingSeat heatingKneeler PadheatingThe heating element that is applied under the seatis a semicircular element, with heating foil as the heatsource, which is designed to radiate heat to people’slegs. In order to prevent overheating the seat, whichcan cause the wood to crack, insulation is appliedbehind the heating foil. So the heat is only radiated tothe wooden floorboard and to the front and back ofthe pew. In order to protect the heating foil, it iscovered with a perforated metal grid that is kept at adistance of 1 cm from the foil with help of spacers.The perforation rate of the metal grid is 50% so the IRradiation from the heating foil can reach the peopledirectly.In one pew, two of these heating elements areapplied, each with an electrical load of 155W. Thespecifications are presented in table 1.2.3 Back heating elementIn the back heating element, the heating foil iscovered on both sides (back and front) with theperforated metal grid that is mentioned before. Themetal grid in this heating element is also kept at adistance of 1 cm from the foil using spacers. Theheating element is attached between the back and theseat; in fact it closes the back of the pew.In each pew, one back heating element is appliedwith an electrical load of 370W.3 Climate room set-upThe measurements discussed in this paper wereused as input parameters for the boundary conditionsof the CFD model. Secondly, these results will beused for the verification of the simulation results.Eventually, the heating system that will be used in thechurch pews will consist of a combination of heatingelements. But to study the effects of each heatingelement on its environment, all measurements wereperformed on one type of heating element in a steadystate indoor environment. This environment wascomposed in the climate chamber of the EindhovenUniversity of Technology.2.2 Kneeler pad elementThe heating element that is applied beneath thekneeler pad consists of a resistance wire (RaychemElectromelt EM2-R) that is double folded. Theresistance of the wire increases when the temperatureof the wire increases. Therefore the wire has a peakload of 970W right after switching on the power anddecreases to 130W when the equilibrium temperatureis reached after about 3 minutes. To preventoverheating the kneeler pad, which can damage thewood, insulation is applied between the electricalresistance wire and the kneeler pad. This combinationof insulation and heating wire is covered with a metalFigure 2. Overview of climate room with the benchesTable 1. Overview of the heating systemsHeatingelementShape Protective cover ofthe elementHeat sourceseat semicircular metal grid,50% openback rectangular metal grid,50% openKneeler rectangular metal sheet Electricalpadresistance wireLength[m]Width[m]Height[m]ElectricalPower[W]#per pewElectrical foil 0.99 Radius = 0.11 155 2Electrical foil 2.00 0.02 0.35 370 12.00 0.09 0.02 130(start peak 970W)1
In this climate room - see figure 2 for thedimensions - a measurement set-up was built aroundthree church pews in which the local heating elementswere applied. The heating elements could be operatedseparately.The heating elements were turned on for 75minutes: it took 15 minutes for the system to heat up,after that the measurements continued for 60 minuteswhich is about the duration of a service. During thesemeasurements, the wall, ceiling and floortemperatures were kept at a temperature of around6°C. The idea behind this temperature was to createan indoor climate that represents the average indoorclimate of the church of Rocca Pietore in theDolomites (northern Italy) during winter.4 Measurement methods4.1 Infrared thermographyInfrared thermography is an appropriate method tomeasure surface temperatures, but not for measuringair temperatures. Because an impression of both airand surface temperatures was desired, paper stripswere fixed to the ceiling, which enabled us to measurethe temperature of the paper. This temperaturerepresents a combination of the local air temperatureand the radiant temperature. Due to its low heatcapacity, paper is suitable for this. Paper strips insteadof a paper plane are used in order to avoid extremedisturbance of the air movement.4.2 Local climateAt first, infrared thermographic pictures weretaken in the climate room. After that, smoke testswere performed to visualize the airflow around thebenches and the heating system. Those two kinds ofmeasurements gave a first impression of the influenceof the local heating system on the temperaturedistribution and air movements between the benches.Figure 3. Measurement grid applied in the plane cutThe positions of the temperature sensors as well as theair velocity sensors were determined on the basis ofthese measurements. The measurements on the localclimate at different locations in a plane cut wereperformed for each heating system. A measuring gridwas applied to this plane cut, see figure 3. (The blackplane is only applied for making the measuring gridvisible on the picture). The air temperature wasmeasured at 16 positions on the measuring grid usingNegative Temperature Coefficient (NTC) sensors.The surface temperature was also measured usingNTCs at 24 positions. Squirrel data loggers wereapplied to register the output of these sensors. AllNTCs were positioned in a way that the influence ofdirect radiation effects was minimized. The airvelocities and turbulence intensities were measuredusing hot sphere anemometers. A configuration thatwas made with a 3-channel Input Module and an A/Dconverter, allowed a simultaneous 10Hz samplingfrequency and storage of the bridge voltage output forall anemometers. The anemometers were placed at the8 most important positions, determined on the basis ofthe performed smoke tests. The hot sphereanemometers were calibrated using the calibrationmethod described by Loomans [4],[5].Figure 4. IR thermograph of the bench with the heatingsystem under the seat turned on.Figure 5. Air flow between the benches with the heatingsystem under the seat turned on.
Page 1: Thermal performance of a local benc

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