Closed Cycle Solar Refrigeration with the Calcium Chloride System

A closed cycle solid absorption intermittent refrigerator, using CaC12 absorbent and NH3 refrigerant, was constructed and tested to obtain the instantaneous and cumulative available overall COP. The combined collector/absorber/generator unit had double glazing of 1.14 m2 exposed areas. The system was fitted with a stagnant passive evaporative condenser with porous sandcrete wall, which produced condenser water temperatures varying from 3 – 10 deg C below ambient, during NH3 generation and condensation.The instantaneous available overall COP rose to a peak which depended on the solar fluxes and starting pressure, as well as on the condenser and ambient temperatures. The peak varied from 0.07 to 0.08. It fell as solar flux decreased towards late afternoon, but rose again slightly due to the combined effect of decreasing collector plate temperature and solar flux. The cumulative overall COP rose steadily to peak values in the range of 0.07 to 0.08, by the end of the generation period. The COP was a strong function of starting generator pressure or evaporating temperature, and fell as the pressure decreased. The cumulative overall COP is much lower than the peak instantaneous COP as a result of system inertia, caused by high collector plate and tube mass, and large system free volume.The refrigerator is capable of maintaining evaporator temperature of -10 OC during the cooling phase, and is well suited for vaccine and food storage applications

Improvement to the Design of a Solid Absorption Solar Refrigerator

The paper presents the highlights of the design of an existing solid absorption solar refrigerator, using CaCl2 stabilised with CaSO4 as the absorbent. The performances are also discussed. The sources of poor performance were identified as high thermal and pressure inertia of the system, high heat loss coefficient, and low absorbent thermal conductivity. Based on these, measures taken in the design of a new model refrigerator, to improve the refrigerator performance are then presented. 

Determination of the Thermophysical Properties of Nsukkanut: A Solid Absorbent for Solar Refrigeration

The thermophysical properties of 'Nsukkanut', - a CaCl2/CaSO4 absorbent mixture used in solid absorption solar refrigeration [1], were studied in this report. The transient experimental technique of Beck and Al-Araji [12] was used in determining the effective thermal conductivity, specific heat and bulk thermal diffusivity of granular (2.8 - 6.35 mm sizes) parkings of the absorbent. Additionally, the parking density crushing stress percentage swell and degree of refrigerant - NH3 absorption were determined. Effective k, c and a values were in the ranges of 0.098 - 0.111 W/mk, 1.123 -1.696 kJ/kg K and 1.404 - 1.053.10-7 m2/s, respectively, for a parking density of 621.4 kg/m3. Average crushing stress, the percentage swell and absorption factor values 018.17 N/mm2, 7.96% and 62.1 % respectively, obtained in this report compared well with values of 8.10 N/mm2, 11.6% and 59.5% correspondingly, as reported in [11].The effect of aluminium as a thermal conductivity improvement additive, on the thermophysical properties of the absorbent, were also studied. For aluminium fractions of up to 3% by mass, no sustained improvement in thermal properties were observed, while the strength and swell properties deteriorated.

Effects of Parallel Channel Interactions, Steam Flow, Liquid Subcool and Channel Heat Addition on Nuclear Reactor Reflood Transients

Tests were performed to examine the effects of parallel channel interactions, steam flow, liquid subcool and channel heat addition on the delivery of liquid from the upper plenum into the channels and lower plenum of Boiling Water Nuclear Power Reactors during reflood transients. Early liquid delivery into the channels, following a loss of Coolant Accident, will help prevent overheating and melt down of the reactor fuel bundles. The tests were performed at the General Electric Nuclear Energy Division Laboratory, California. The channels consisted of two 5.22m long *25.4mm long*23.6mm i.d. stainless steel tubes, with unequal orificing at the bottom, and equal orificing at the top. Provisions were made for electrical resistance heating of 3.5m of each tube, and for visual observation of flows through the tubes. Test fluids were steam and saturated or subcooled water. Subcools ranged from 3.3 deg C to 37.2 deg C, and system pressures varied from near atmospheric to a little over 1.7 bar. Test section heat fluxes were between 2.58 and 13.95 KW/m2. It was observed that channel heat additions tended to make each tube behave independently of the other. As a result of subcool and vapour condensation, vapour supply into the lower plenum increased liquid delivery into the channels, and decreased the system rewet and reflood times when the subcool was in excess of about 20 deg C. Parallel channel interactions were observed to produce co-current downflow in the less restricted tube, with counter-current flow existing in the more restricted tube. This is desirable. When conditions permitted, the interactions gave rise to the classical "steam bound" flow configuration - (i.e. water hold up in the upper plenum due to top orifice Counter Current Flow Limitation, partial filling of the more restricted channels, a partially full lower plenum, and pure vapour flow in the less restricted channel). This configuration is undesirable for thermal recovery of a reactor following a loss of coolant accident

Effect of Crude Oil on Permeability Properties of the Soil

The impact of crude oil on the permeability of the soil in a non oil producing community in Enugu State was investigated using disturbed A 6 CL soil sample collected from Ibagwa Nike area of the state. The sample was divided into five 5 portions and each of the four 4 portions was dosed with Bonny light crude oil at 2 , 4 , 6 and 8 by weight of the samples. The physical properties of the uncontaminated soil were tested and analyses and used as control. The aim of the laboratory investigation was to determine the effects of crude oil on the permeability of the soil. The permeability of the uncontaminated soil was found to be 1.2609x10 7. Permeability tests were also conducted on the contaminated soil samples at the various percentage contaminations. The results showed that at 2 crude oil contamination the permeability was 9.6403x10 9, a drastic reduction. The other results were 6.9600x10 6, 2.2621x10 8 and 9.1286x10 8 at 4 , 6 , and 8 contamination levels, respectively. The ranking after contamination is seen to drop within the range of 10 8 and 10 9 showing a change in the permeability due to oil content. This observed reduction in permeability alters the natural groundwater recharge which can be remedied by enhanced bioremediation through aeration of the soil. Iloeje A. F. | Aniago V. "Effect of Crude Oil on Permeability Properties of the Soil" Published in International Journal of Trend in Scientific Research and Development (ijtsrd), ISSN: 2456-6470, Volume-1 | Issue-1 , December 201

Two Phase Flow Split Model for Parallel Channels

A model has been developed for the determination of two phase flow distributions between multiple parallel channels which communicate between a common upper and a common lower plenum. It utilizes the requirement of equal plenum to plenum pressure drops through the channels, continuity equations at the lower plenum channel intake boundaries, together with phase-split relationships at the channel inlets, to set up a series of nonlinear simultaneous equations. The equations are solved using the Broyden’smethod [4], a modification of the Newton’s method. The model and code are capable of handling single and two phase flows, steady states and transients, up to ten parallel flow paths, simple and complicated geometries, including the boilers of fossil steam generators and nuclear power plants. A test calculation has been made with a simplified three-channel system subjected to a two-phase flow transient, and the results have been very encouraging

Behavioral problems of siblings of epileptic children in Enugu

Background and Objective: The existence of a psychosocial dysfunction in the siblings of children with chronic illness has been documented. There are very few reports on siblings of children with epilepsy. The aim of this study is to investigate to what extent the children’s epilepsy has affected their healthy siblings in our own center.Materials and Methods: Epileptic patients who consecutively referred to the Pediatric Neurology Clinic of the University of Nigeria Teaching Hospital, Enugu, from October 1999 to September 2000 were recruited. Demographic data were obtained, with a questionnaire administered to the parents. Information on the behavior of the school-age siblings and control was obtained by the class teachers using Rutter’s behavior scale (B2) for children (Teacher’s Scale).Results: One hundred and fifty-six children with epilepsy, of age four to fifteen years, 124 males and 32 females, with a Male: Female ratio of 4: 1, were recruited; and 156 school-age siblings of the epileptic children (index children) and 156 controls were studied. Prevalence of behavioral problems was 38.5 and 15.4%, respectively, among the index and control children (P < 0.001). There was no significant sex difference in the two groups. There was a significant difference in the distribution of the types of behavior problems between the index and controls (P < 0.05). The duration of epilepsy did not affect the prevalence of behavior problems (P < 0.05), but seizure control had a significant effect on the prevalence of behavior problems (P < 0.001).Conclusions: Siblings of children with epilepsy have more behavioral disturbances than controls. A strong association was found between poor seizure control and the prevalence of behavioral problems

Three-Step Model of Dispersed Flow Heat Transfer (Post CHF Vertical Flow)

The paper presents a three step model of the dispersed flow heat transfer process, using an analysis of a single drop motion and heat transfer, and a statistical representation of the overall behaviour of the drops. The resulting equation gives the total heat transferred to the flow in terms of the mass flux, flow quality, fluid properties, wall roughness, and wall superheat. It includes the effect of contact angle or change in the wet ability of the surface. The range of validity of the model and the equation extends from dry wall film boiling to transition boiling, and is limited on the low temperature end by the critical Heat Flux region. Since the equation is analytically derived, its differentiation with respect to wall superheat will yield the Minimum Heat Flux point. The equation and model provide a very powerful base for analysis and prediction of post Critical Heat Flux heat transfer. The stable film boiling data for dispersed vertical flow of liquid nitrogen from reference [1] have been compared with the prediction and the results have been favourable

Severity of motor dysfunction in children with cerebral palsy seen in Enugu, Nigeria

Introduction: Children with cerebral palsy (CP) have gross motor dysfunction (GMD) of varying degrees of severity. The Gross Motor Function Classification System (GMFCS) is widely used internationally to classify children with CP into functional severity levels. There are few reports on the use of GMFCS in Nigeria to determine the severity of motor dysfunction in children with CP. This study aims to classify children with CP in Enugu on the basis of severity of their GMD in order to ascertain their management needs.Methods: The study was a cross sectional observational study and sample selection was by consecutive recruitment. One hundred (100) children with CP aged 9 – 96 months, attending two Pediatric Neurology Clinics in Enugu, were consecutively recruited. Relevant history was taken including modalities of treatment received. Neurological examination was done and the GMFCS manual was used to classify the children into levels of severity.Results: GMD varied in severity in the patients from mild (47%) (GMFCS levels I & II) to moderate (7%) (GMFCS levels III) and to severe (46%) (GMFCS levels IV & V). Those in levels I – III (54%) were ambulatory while those in levels IV & V (46%) were non-ambulatory. Of the 53 that required mobility assistive device, only 6 (11.3%) were using one.Conclusion: More than half of CP patients seen in Enugu were ambulatory with mild to moderate motor dysfunction based on the GMFCS. Only a few of our patients are appropriately rehabilitated with augmentative interventions.Keywords: Severity, gross motor dysfunction, GMFCS, Enugu, cerebral palsy, managemen