Summary In this study, a vapor‐compression cooling system utilizing different phase change materials (PCMs) has been studied whereby the electricity consumption peak load is shifted. More specifically, the dynamic performance of cooling systems with and without using PCM is evaluated for the hottest day of the year. The proposed system uses the cooling energy to freeze, or “discharge” the PCM during nighttime when the cooling load is minimally needed and uses the stored thermal energy during the peak load hours by melting, or “charging” the PCM. This leads to better performance during peak load hours when higher cooling loads are needed. Different PCMs including oleic acid, SP224A, CL, CaCl2·6H2O have been investigated. The system performance has been investigated by considering several parameters such as coefficient of performance, compressor power consumption, accessible cooling load, and melting fraction of PCM. The effect of different volumes of PCM on the average cooling cost has been evaluated, as well. The results indicated that with using the PCM, the accessible cooling load raises and the electricity consumption falls during hours of the peak load. Peak load reduction in the on‐peak period is different for various PCMs. In comparison with the conventional cooling system, the peak load alters from 315 W to 170, 164, 93, and 74 W for CL, oleic acid, CaCl2·6H2O, and SP224A, respectively. The evaluation of different PCM illustrated that for the volume of 150 L, the peak load shaving for SP224A is the most value which is 76.3%. Moreover, while the volume of different PCMs increases, the average price of the cooling energy decreases, and the Levelized cost of cooling energy rises.

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Background:To determine patient orthodontic treatment need, appropriate self-perceived indices are required. The aim of this study was to assess the sensitivity and specificity of esthetic component (AC) of the index of orthodontic treatment need (IOTN), oral esthetic subjective index scale (OASIS), and visual analog scale (VAS) through dental health component (DHC) IOTN as a normative index to determine the more appropriate self-perceived index among young adults.Materials and Methods:In this cross-sectional study, a sample of 993 was randomly selected from freshman students of Isfahan University. Those with a history of orthodontic treatment or current treatment were excluded. DHC was evaluated by two inter- and intra-calibrated examiners. Data for AC, OASIS, and VAS were collected through a questionnaire completed by students. Descriptive statistics, Mann–Whitney U-test, and Spearman correlation test, were used for data analyses. Sensitivity, specificity, positive and negative predictive values of self-perceived indices were calculated through DHC.Results:Sensitivity of AC, OASIS, and VAS for evaluating definite orthodontic treatment need was calculated at 15.4%, 22.3%, and 44.6%, respectively. Specificity of these indices for evaluating definite orthodontic treatment need was calculated at 92.7%, 90.5%, and 76.2% percent, respectively. All self-perceived indices had a significant correlation with together and with DHC (P < 0.01). Among demographic factors, there was weak but significant correlation only between mother's educational level and VAS (P < 0.01).Conclusion:Due to the sensitivity and specificity of the three self-perceived indices, these indices are not recommended for population screening and should be used as adjuncts to a normative index for decision-making in orthodontic treatment planning.

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