A Numerical Simulation of the Effect of Ambient Temperature on Capillary Tube Performance in Domestic Split Air Conditioners with R22 Alternatives

A numerical model has been formulated to simulate the capillary tube insplit air conditioners of 1 and 2 TR capacities under high outdoor air temperatures. The outdoor air temperature was varied from 35 to 55°C with 5 °Cincrements. Three environment friendly refrigerantswereused as alternatives to R22. They are  R290, R407C and R410A. Finite difference method has been adopted in conjunction with EES software. This model is capable of predicting pressure, temperature, quality, velocityandviscositydistributions through the capillary tube for all refrigerants. The geometrical parameters and input conditions to the capillary tube model areextracted from experimental data.  Theseinclude inner diameter, mass flow rate, surface roughness, temperature and pressure of the subcooledliquid refrigerant.  Theresults show that the capillary choking length increases with increasing outdoor air temperature.    Results of the simulation show thatR290 needsmore capillary length than the other refrigerants investigated,whereas  R410A needs less capillary tube length. Keywords: Capillary tube simulation; capillary tube with R22,R290, R407C, R410A; high ambient effect on capillary tube

SIMULATION OF INDIRECT EVAPORATIVE COOLER HEAT EXCHANGER AT IRAQI CONDITIONS

The investigation included PHE performance variation with heat exchanger dimensions, plate spacing, inlet air velocities and inlet air temperatures. The momentum and energy equations were solved in 3-dimensions by using FLUENT 5.3 software and heat exchanger performance parameters were extracted from the post processing of the numerical data. In addition, a 2-dimensional fluid flow and heat transfer numerical analysis for the crossflow PHE was carried out. A numerical code based on the finite difference method and the SIMPLE algorithm was developed to solve the governing equations. The result of the numerical study for PHE performance shows that for both air streams the maximum thermal gradient occurs at 0.5 m/s inlet air velocity while the minimum occurs at 5 m/s velocity. Furthermore; the greater thermal gradient for the both air streams occurs at 3 mm plate spacing and decrease progressively to the lowest gradient at 10 mm spacing. Also, the results indicated that indirect evaporative cooling could be applied to obtain suitable outlet air temperatures for low and medium values of wet-bulb temperatures in arid climates

EXPERIMENTAL INVESTIGATION OF INDIVIDUAL EVACUATED TUBE HEAT PIPE SOLAR WATER HEATING SYSTEMS

lar water heating systems with heat pipes of three diameter groups of 16, 22 and 28.5 mm. The first and third groups had evaporator lengths of 1150, 1300 and 1550 mm. The second group had an additional length of 1800 mm. all heat pipes were of fixed condenser length of 200 mm. Ethanol at 50% fill charge ratio of the evaporator volume was used as the heat pipes working fluid. Each heat pipe condenser section was inserted in a storage tank and the evaporator section inserted into an evacuated glass tube of the Owens- Illinois type. The combined heat pipe and evacuated glass tube form an active solar collector of a unique design. The resulting ten solar water heating systems were tested outdoors under the meteorological conditions of Baghdad, Iraq. Experiments were carried out with no load, intermittent and continuous load conditions. Some tests, at no load, were carried out with and without reflectors. The overall system efficiency was found to improve with load conditions by a maximum of 55%. The system employing an 1800 mm evaporator length and 22 mm heat pipe (HP7) showed the best performance by higher water temperatures, overall useful energy gain and efficiency at various load conditions. System performance was predicted theoretically using electrical analogy derived from an energy balance. An agreement of within 14% was obtained between theoretical and experimental values

Thermal Topographical Rings as a New Tool for Laser Eye Surgery

Abstract Measurement of the corneal surface temperature during the laser surgery have been modified at the last few years, to be used as an extra useful monitoring tool during the dynamic ablation process. While the concentric Placido rings have been used before to measure the refractive errors, here, it have been modified to be used as a new suggested tool to study the thermal response upon the anterior corneal surface during laser eye surgeries. The thermal infrared camera was used to get an image captured at the end of the treatment, where contours with isotherms are derived and examined. The new contour lines introduce the temperature induced per location upon the corneal surface and reflect the biomechanical response behavior. Comparing the contour image with the image generated by the treatment system for the ablated depth showed a new indication for safety limits especially the effect of decentration and other irregular aberrations

Adapting evidence-based clinical practice guidelines for people with attention deficit hyperactivity disorder in Saudi Arabia: process and outputs of a national initiative

Abstract Background We recently adapted the published National Institute for Health and Care Excellence (NICE) Attention deficit hyperactivity disorder (ADHD) diagnosis and management guideline to the Saudi Arabian context. It has been postulated that adaptation of evidence-based clinical practice guidelines to the local healthcare context rather than de-novo development will improve their adoption and implementation without imposing a significant burden on resources. The objective of this paper is to describe the adaptation process methodology utilized for the generation of the first national guideline for management of people with ADHD in Saudi Arabia. Methods We used the KSU-Modified-ADAPTE methodology for the guideline adaptation process. We describe the full process in detail including the three phases of set-up, adaptation, and finalization. The process was conducted by a multidisciplinary guideline adaptation group in addition to an external review for the clinical content and methodology. Results The group adapted ten main categories of recommendations from one source CPG (NICE). The recommendations include: (i) service organisation and training, (ii) recognition, identification and referral, (iii) diagnosis, (iv) support, (v) managing ADHD, (vi) dietary advice, (vii) medication, (viii) maintenance and monitoring, (ix) adherence to treatment, and (x) review of medication and discontinuation. Several implementation tools were compiled and developed to enhance implementability including a clinical algorithm, quality measures, coding system, medication tables, translations, patient information, and online resources. Conclusions The finalized clinical practice guideline provides healthcare providers with applicable evidence-based guidance for the management of people with ADHD in Saudi Arabia. The project also demonstrated the effectiveness of KSU-Modified-ADAPTE, and emphasized the value of a collaborative clinical and methodological expert group for adaptation of national guidelines.http://deepblue.lib.umich.edu/bitstream/2027.42/173676/1/13034_2020_Article_351.pd