Coupled TRNSYS-CFD simulations evaluating the performance of PCM plate heat exchangers in an Airport Terminal building displacement conditioning system

This is the post-print version of the Article. The official published version can be accessed from the link below. Copyright @ 2013 Elsevier.This paper reports on the energy performance evaluation of a displacement ventilation (DV) system in an airport departure hall, with a conventional DV diffuser and a diffuser retrofitted with a phase change material storage heat exchanger (PCM-HX). A TRNSYS-CFD quasi-dynamic coupled simulation method was employed for the analysis, whereby TRNSYS® simulates the HVAC and PID control system and ANSYS FLUENT® is used to simulate the airflow inside the airport terminal space. The PCM-HX is also simulated in CFD, and is integrated into the overall model as a secondary coupled component in the TRNSYS interface. Different night charging strategies of the PCM-HX were investigated and compared with the conventional DV diffuser. The results show that: i) the displacement ventilation system is more efficient for cooling than heating a space; ii) the addition of a PCM-HX system reduces the heating energy requirements during the intermediate and summer periods for specific night charging strategies, whereas winter heating energy remains unaffected; iii) the PCM-HX reduces cooling energy requirements, and; iv) maximum energy savings of 34% are possible with the deployment of PCM-HX retrofitted DV diffuser.This work was funded by the UK Engineering and Physical Sciences Research Council (EPSRC), Grant No: EP/H004181/1

Effect of ambient conditions on the first and second law performance of an open desiccant cooling process

An open desiccant cooling process is presented and applied to ventilation and recirculation modes of the system operation. The cooling system consists of a desiccant wheel, a rotary regenerator, two evaporative coolers, and a heating unit. Certain ideal operating characteristics based primarily on the first, law of thermodynamics are assumed for each component. The system with indoor and outdoor A RI conditions has a thermal coefficient of performance (COP) of 1.17 in ventilation mode and 1.28 in recirculation mode. A second law analysis is also performed and at ARI conditions, the reversible COP of the system is determined to be 2.63 in ventilation mode and 3.04 in recirculation mode. Variation of the first and second law based COP terms and cooling load with respect to ambient temperature and relative humidity are investigated in both modes or the system operation. The results of the analysis provide an upper limit for the system performance at various ambient conditions and may serve as a model to which actual desiccant cooling systems may be compared. As an additional study, a non-ideal system operation is considered and it is determined that both the COP and cooling load decrease with increasing ambient temperature and relative humidity, and they approach zero at high values of ambient temperature and humidity. (c) 2006 Elsevier Ltd. All rights reserved

The correlation between the electroencephalographic spectral analysis and salivary cortisol rhythm in insomnia

Objective Insomnia is a common sleep disorder that affects many adults either transiently or chronically. This study aimed to establish whether there is a relationship between the electroencephalographic (EEG) spectral analysis and salivary cortisol levels in insomnia and compared to healthy controls. Materials and methods This case-control study included 15 insomnia patients and 15 healthy control subjects. Insomnia was determined according to the International Classification of Headache Disorders III diagnostic criteria. The EEG data were collected and processed with MATLAB software. Blood and salivary samples were taken for hematological and biochemical measurements. Salivary cortisol levels were calculated and compared statistically with the healthy group. Results The mean age of the patients was 46.5 +/- 11 years. The salivary cortisol levels at 18:00 and 24:00 were found higher in the insomnia than in the healthy subjects (respectively, 0.12 (0.11) mu g/dl, 0.07 (0.02) mu g/dl). But this difference was not statistically significant (p > 0.05). No significant difference was observed in the spectral analysis of patients between the frontal, central, and occipital channel (p > 0.05). However, in the correlation between the frontal channel spectral analysis and at the 24:00 salivary cortisol of patient and control group, DeltaGmax (p = 0.002), DeltaGmean (p = 0.019) and, in the correlation with 18:00 salivary cortisol DeltaGmax (p = 0.010), were positively correlated. Conclusion In this study, no significant difference was found in spectral analysis and salivary cortisol levels in insomnia patients, but at 18:00 and 24:00, cortisol levels were correlated positively with theta and delta waves in EEG spectral analysis in some channels

Evaluation of pituitary function and metabolic parameters in patients with traumatic maxillofacial fractures

Purpose: This study was designed to assess the pituitary functions of patients with traumatic maxillofacial fractures and compare the results with healthy controls. Methods: Thirty patients (mean age, 38.14 ± 14.15 years; twenty-six male, four female) with a traumatic maxillofacial fracture at least 12 months ago (mean 27.5 ± 6.5 months) and thirty healthy controls (mean age, 42.77 ± 11.36 years; twenty-five male, five female) were included. None of the patients were unconscious following head trauma, and none required hospitalization in intensive care. Basal pituitary hormone levels of the patients were evaluated. All patients and controls had a glucagon stimulation test and an ACTH stimulation test to evaluate the hypothalamic–pituitary–adrenal axis and the GH–IGF-1 axis. Results: Five of thirty patients (16.6%) had isolated growth hormone (GH) deficiency based on a glucagon stimulation test (GST). The mean peak GH level after GST in patients with hypopituitarism (0.54 ng/ml) was significantly lower than those without hypopituitarism (7.01 ng/ml) and healthy controls (11.70 ng/ml) (P < 0.001). No anterior pituitary hormone deficiency was found in the patients, except for GH. Conclusion: Our study is the first to evaluate the presence of hypopituitarism in patients with traumatic maxillofacial fractures. Preliminary findings suggest that hypopituitarism and GH deficiency pose significant risks to these patients, particularly during the chronic phase of their trauma. However, these findings need to be validated in larger scale prospective studies with more patients