Performance of solid desiccants for fixed-bed regenerator applications

Fixed-bed regenerators (FBRs) are a relatively novel type of energy recovery ventilator (ERV) used to reduce energy consumption in buildings. FBRs operate under cyclical conditions by storing heat and moisture in one recovery period and transferring the accumulated heat and moisture to an air stream in the next period. FBRs are very promising for heat recovery but are yet to be fully adapted for moisture transfer on a commercial scale. In order to enable moisture transfer, adsorptive materials known as desiccants can be coated on FBR plates for energy recovery. The primary goal of this thesis is to apply experimental and numerical methods to select desiccants for FBRs. Desiccants remove moisture by an adsorption process as opposed to absorption where molecules penetrate a bulk media. The sorption properties of the desiccant directly influence the latent effectiveness of FBRs during summer operation. The experimental results in this thesis showed that sorption kinetics is an important parameter for FBRs. A numerical model which includes the sorption kinetics was used to predict the dynamic behaviour of FBRs. The numerical results showed that selecting desiccants with a higher kinetic rate constant value leads to higher moisture transfer rates which in turn will increase the effectiveness of FBRs. The main contribution of this thesis is that the results enable researchers to determine the recovery periods and parameters when sorption kinetics can be neglected, and an equilibrium model is acceptable for FBR applications. The results showed that a 5% relative error in latent effectiveness was achieved in the equilibrium model for a rate constant of at least 0.0014 1/s, thicknesses of up to 25 mm, effective diffusion coefficient of at least 2.9 × 10-5 m2/s, and cycle periods of at least 60 s

Awareness, Treatment, and Control of Hypertension in Primary Health Care and Secondary Referral Medical Outpatient Clinic Settings at Enugu, Southeast Nigeria

Essential hypertension is the most common noncommunicable disease (NCD), affecting more than half the adult population in many countries and being the major NCD contributor to the double burden of disease in developing countries. We undertook a survey of the hypertension awareness, treatment, and control in primary and secondary referral health care clinics in Enugu, Nigeria, and compared these data with those obtained in local community surveys. The prevalence of hypertension in the primary care clinic (9.2%) was lower than in a previously reported community survey (42.2%), while, in the referral clinic, 70.3% of patients attending were hypertensive. Hypertension awareness rates were 91.9%, 29.4%, and 93.2% in these respective health care settings. Treatment and control rates (89.9% and 72.9%) were better in the secondary care clinic than in the primary care centre (87.7% and 46.0%). (Chi-square analysis confirmed statistically significant differences between these rates (p<0.05).) These data may form a useful index of health care system effectiveness in Nigeria. Possible reasons for the differences observed and effective strategies to address the waxing pandemic of hypertension are discussed