# Experimental and Theoretical Study of Heat Transfer in a Chilled Ceiling System
## 5 Results and Discussion  
According to the data, which are explained in the section on the Experimental Methodology, the experiments were carried out with 48 different variations at four different water temperatures, three different water flow rates and four different heat sources. To verify the experiments, experiment 33 was repeated on three different days under the same conditions, and the same results were obtained. For when the water flow temperature was kept constant at 14.15 \({}^{\circ}\)C, the water flow rate was varied among 0.54 m\({}^{3}\)/h, 0.93 m\({}^{3}\)/h and 1.10 m\({}^{3}\)/h and the heat supplied to the room was changed to 0 W, 280 W, 500 W and 780 W, the observed change in room temperature is shown in Figure 11.  
Figure 11: Time-dependent change in room air temperature with different heat rates and water flow rates (\(\Gamma_{\rm water-supply}\)) = 14.15 \({}^{\circ}\)C in the case of constant water temperature). Figure 11 shows the relationship between water flow temperature, water flow rate, heat rate and room temperature. As can be seen, as the water flow rate increases, the room temperature decreases rapidly. It has been observed that for the same heat rate and water flow temperatures, the room temperature decreases to lower temperatures as the water flow rate increases. In the experimental studies, it was observed that the relative humidity in the room varied between 35 and 50% Rh, and no condensation occurred during the experiments. In Figure 11, it is seen that in all experiments where the chilled ceiling room system was used, the room temperature decreased over time, showing the same trend. It was concluded that with high heat rates, the room temperature increases for the first 30 min and then decreases and enters a stable regime, while with low heat rates, the room temperature constantly decreases. It is understood from Figure 11 that the effect of the increase in water flow rate on the decrease in room temperature is more effective at low heat rates. In this study, the heat transfer rate and convection coefficient values for experiments providing the desired environmental conditions were calculated, and their comparison with the values reported in the literature [8] are shown in Table 6.  
According to the results of the experiments, there is an increase in cooling capacity when the water flow rate is increased from 0.54 m\({}^{3}\)/h to 1.10 m\({}^{3}\)/h; when the heat load in the room is increased from 0 W to 780 W, there is a decrease in cooling capacity; and when the water temperature is reduced from 18 \({}^{\circ}\)C to 14 \({}^{\circ}\)C, an increase in cooling capacity was observed. The experimental results indicated that with a heat rate of 280 Watts and the lowest supply water temperature of 14 \({}^{\circ}\)C, indoor comfort conditions were achieved with water flow rates of 0.93 m\({}^{3}\)/h and 1.10 m\({}^{3}\)/h, respectively. When comparing the heat transfer coefficient values, it was found that the radiation and convection heat transfer coefficients were within the reference range reported in the literature. In the literature, values of 3.1-4.1 W/(m\({}^{2}\)K) have been specified for h\({}_{\rm c}\). The h\({}_{\rm c}\) value obtained in this study is 4.02 W/(m\({}^{2}\)K) and is compatible with that in the literature. In the literature, values of 5.5 W/(m\({}^{2}\)K) have been specified for hr. The \(h_{r}\) value obtained as a result of this study is 5.49 W/(m\({}^{2}\)K) and is compatible with that in the literature. Figure 12 shows the temperature change in the test room when the water flow temperature is kept constant at 14.42 \({}^{\circ}\)C, the water flow rate is kept constant at 0.54 m\({}^{3}\)/h, and the heat supplied to the room is changed to Q\({}_{1}\) = 0 W, Q\({}_{2}\) = 280 W, Q\({}_{3}\) = 500 W and Q\({}_{4}\) = 780 W. The dashed horizontal line in Figure 12 represents the comfort limit shown in the ASHRAE Comfort Zone Graph.