# Investigation on an Improved Household Refrigerator for Energy Saving of Residential Buildings
## 5 Results and Discussion
### Performances at Different Heat Pipe Design
The temperature of heat pipes is closely related with its installation position in the freezer walls, and the cold loss reduction behavior of the side freezer walls is relatively more stable, even if the location  
Figure 12: Heat transfer characteristics of the heat pipes at \(A_{eva}\). Figure 13: Behaviors of improved refrigerator versus at various \(A_{eva}\). of heat pipes changes. Correspondingly, Figure 15 shows the overall behaviors of the modified freezer with increasing \(X_{in}\). Cold loss of the modified freezer (C) slightly drops from 7.3 W to 7.6 W, and cold loss reduction ratio (\(\eta_{re}\)) decreases from 12.1% to 8.9% as \(X_{in}\) increases from 10% to 25%. The overall cold loss recovery amounts of heat pipes at various installation positions remain relatively stable. These results certify the reliability of the energy saving function of the improved refrigerator. Furthermore, the locations of the condensing sections of heat pipes in the side and the topside freezer walls are individually varied, and the behaviors of the improved refrigerator are evaluated to reveal the energy saving difference at the side and the topside freezer walls. The ratio of wall thickness inside of heat pipes to the whole side wall thickness (\(X_{s,in}\)) is varied from 10% to 25%, while that for topside freezer wall (\(X_{t,in}\)) is fixed to 16%, and the calculated results are shown in Figure 16. \(T_{HP}\) raises from \(-1.8\)\({}^{\circ}\)C to 0.5 \({}^{\circ}\)C, \(\eta_{re}\) decreases from 11.7% to 9.4%, and their variation ranges are smaller compared with the operating states with changing \(X_{s,in}\) and \(X_{t,in}\) together (shown in Figures 14 and 15). In particular, \(\eta_{s,re}\) drops from 19.4% to 11.1% whereas \(\eta_{t,re}\) raises from 16.8% to 24.0%. The temperature distribution at the topside freezer wall is affected by the raising \(T_{HP}\), and thus its cold loss drops, even if \(X_{t,in}\) is constant. For comparison, the behavior of the improved refrigerator is shown in Figure 17 as \(X_{t,in}\) is varied from 10% to 25% with a fixed \(X_{s,in}\). Correspondingly, \(\eta_{s,re}\) increases from 16.0% to 18.2%, \(\eta_{t,re}\) reduces from 23.7% to 13.6%, \(T_{HP}\) slightly raises from \(-1.0\)\({}^{\circ}\)C to \(-0.3\)\({}^{\circ}\)C, and \(\eta_{re}\) decreases from 11.5% to 10.5%. The performance responses to the variation of \(X_{t,in}\) are much weaker than those of  
Figure 14: Temperatures of heat pipes and cold reduction ratios of side and topside freezer walls at various \(X_{in}\). Figure 15: Overall cold loss of the modified freezer and cold loss reduction ratio versus \(X_{in}\). \(X_{s,in}\), which indicates the location of condensing sections of heat pipes at the topside freezer wall plays a more important role. Generally, properly adjusting the location of condensing sections of heat pipes at each freezer can vary the cold loss recovery capability of the improved refrigerator, and the energy saving design is feasible as \(X_{s,in}\) and \(X_{t,in}\) are changed between 10% to 25%.