Improved latent heat storage properties through mesopore enrichment of a zeolitic shape stabilizer

Latent heat storage systems are applied to keep temperature of a local environment within a constant range. The process takes place via release/storage of latent heat during freezing/melting of a corresponding phase change material embedded in a shape stabilizer, which is the scaffold keeping the phase change material stationary in its molten form. In this work, a highly siliceous ZSM-5 and modified versions thereof were chosen as shape stabilizers for molecular and polymeric phase change materials (namely lauric acid and polyethylene glycol), to be impregnated using solvent assisted vacuum impregnation. The dominantly microporous analogues, parent ZSM-5 and its acid-treated derivative, were limited to 40% uptake for each phase change material. Contrastingly, a mesopore rich analogue (as formed under basic conditions) reached 65% impregnation for lauric acid and 70% for polyethylene glycol, without any leakage at 70 \ub0C, resulting in latent heats of 106.9 J/g and 118.6 J/g for each composite, respectively. A simple prototypical real-world application demonstrated that the prepared lauric acid and polyethylene glycol composites of mesopore enriched ZSM-5 could maintain their temperatures up to 27% and 22% lower than the ambient environment under solar heating, as well as up to 20% and 26% higher when solar heating stops. The presented findings indicate mesopore enrichment improves phase change material uptake in these low cost, non-toxic zeolitic shape stabilizers, hence making them good candidates as isolation materials to address energy loss during heating/cooling of household environments

Performance improvement potential of a PV/T integrated dual-source heat pump unit with a pressure booster ejector

Dual-source heat pump unit can utilize the evaporation of the refrigerant at two different pressures. By adopting an ejector, high-pressure refrigerant stream can be used to lift compressor inlet pressure which results in a higher coefficient of performance (COP). This study proposes a renewable energy sourced and high-efficiency heat pump system which can be easily building integrated to offer a renewable heating solution. The system is devised on the complementation of dual thermal sources; one is air and the other one is solar, to maximize the utilization of ambient energy for highly efficient operation of heat pump. Using the advantage of the relatively lower operating temperature in the solar collector line, the thermal efficiency of the collector would be sufficient in winter. Adaptation of photovoltaics in the collector as a PV/T unit, will benefit the system from the produced electricity for further reduction of the demand from the grid. Along with the use of PV/T collector, the system can be potentially carbon neutral for larger collector areas. In this study, the performance improvement potential of a dual-sourced heat pump unit with an ejector as a booster is investigated for different locations in Turkey which presents different solar and weather profiles. The optimum collector evaporation temperatures are determined, and COP improvement potentials are discussed for different conditions. For a heating supply of 5 kW, the COP of the system can be improved by 22.6% under 400 W/m2 and 10°C ambient using 15 m2 PV/T collector. Including the electricity generated from the PV, reduction of the electricity demand from the grid can reach to 75% for the same conditions

Corneal topographic changes in premenopausal and postmenopausal women

<p>Abstract</p> <p>Background</p> <p>To asses the effect of menopause on the corneal curvature changes using corneal computerized videokeratography (CVK) in premenopausal and postmenopausal healthy women.</p> <p>Methods</p> <p>Thirty-six postmenopausal women with mean ages of 49.2 (range 39 to 57) were enrolled in this randomized, prospective study, comparing with 26 healthy controls with mean ages of 38.5 +/- 4.9 (range 32 to 49). Subjects were determined to be postmenopausal, by the Gynecology and Obstetrics Department, based on blood Follicular Stimulating Hormone (FSH), Luteinizing Hormone (LH), Estradiol, Progesterone levels and clinical complaints. Complete ophthalmic examination and CVK using Haag-Streit System was performed in both premenopausal and postmenopausal women.</p> <p>Results</p> <p>Mean horizontal curvature and vertical curvature of central corneal power in premenopausal women were 43.5 +/- 1.25 Diopter (D), and 44.1 +/- 1.53 D. Mean horizontal curvature and vertical curvature of central corneal power in postmenopausal women were 43.9 +/- 1.4 D, and 44.6 +/- 1.3 D. The mean keratometric astigmatisms of premenopausal and postmenopausal women were 0.81 +/- 0.57 D (4–179 degrees), 0.74 degrees +/- 0.5 D (1–180 degrees) respectively. No significant corneal curvature changes were detected between premenopausal and postmenopausal groups (P > 0.05). On the other hand, we only found negative but significant correlation between horizontal corneal curvature and estrogen level of postmenopausal women (r = -0.346, p = 0.038).</p> <p>Conclusion</p> <p>Menopause is physiologic process and may also affect corneal topographic changes. In postmenopausal women, corneal steeping was observed minimally compared to premenopausal women. The results suggest that changes in estrogen level of women with menopause are associated with slightly alteration of horizontal curvature of cornea.</p

QALY: Quality Adjusted Life Year

Nufusun yaslanmasi ve yaslilik donemi hastaliklar ile kronik hastaliklarin one cikmasi verilen saglik hizmetlerinin sadece saglik duzeyi uzerine degil yasam kalitesine etkisinin de onemli bir cikti olarak degerlendirilmesini getirmistir. Aslinda bu yaklasim Dunya Saglik Orgutunun (WHO), 1946 yilinda sagligi &#8220;yalnizca hastalik ve sakatligin olmayisi degil, fiziksel, ruhsal ve sosyal yonden tam bir iyilik hali&#8221; olarak tanimlamasina uyan ve bu ogeleri daha tam ve kapsamli karsilayan bir yaklasim olmustur. QALY (Quality Adjusted Life Year), &#8220;Kaliteye Ayarli Yasam Yili&#8221; anlamina gelen sozcuklerin kisaltmasindan olusmaktadir. Her bir omur senesini yasam kalitesi ile birlikte ele alan bir olcektir. Hem yasam beklentisindeki artisi, hem de yasam kalitesindeki farklilasmayi olcer. Amac, bircok farkli durumdaki saglik kazanimlarinin ortak bir olcekle degerlendirilerek basit bir birimle ifade edilmesi ve bircok boyutun tek bir endekste toplanmasidir. QALY terimi sinirli saglik kaynaklarinin alternatif saglik programlari arasinda dagitilmasi sirasinda karar vericilere yardimci olan analizlerde kazanimlarin verimliligini daha dogru olcmek icin gelistirilmis bir kavramdir. Saglik hizmetleri finansmaninda kullanilan kaynaklar, dunyadaki diger ulkelerde oldugu gibi ulkemizde de sinirlidir. Mevcut kaynaklarin yetersizligi, bunlarin mumkun olan en iyi sekilde kullanilmasi sorumlulugunu da beraberinde getirmektedir. [Med-Science 2012; 1(3.000): 232-243

Performance improvement potentials of low global warming potential refrigerants for intercity bus air conditioning system

In this study, theoretical investigation of two evaporator ejector refrigeration system was carried out based on energy and exergy analysis using R134a and low global warming potential refrigerants (namely R1234yf and R1234ze(E)). In order to perform the analyses, a simulation model was developed and then the influence of different parameters on the COP, COP increase rate and exergy destructions were discussed for each refrigerant. The model was validated with experi¬mental data for R134a and later used to predict the behavior with R1234yf and R1234ze(E). It was found that the highest exergy destruction occurs in the R1234yf system and the increase rate in the COP with respect to the conventional system by using ejector as an expansion device are 15% for R134a, about 17% for R1234yf and about 15% for R1234ze(E), respectively