scholarly journals Theoretical and Experimental Behaviour of Single Slope Solar Still Heat Transfer

2017 ◽  
Vol 4 (1) ◽  
pp. 100-112
Author(s):  
Yeo Kiam Beng ◽  
Ong Cheah Meng ◽  
Seock-Sam Kim
Keyword(s):  
Heat Transfer ◽  
Theoretical Model ◽  
Maximum Output ◽  
Solar Still ◽  
Consistent System ◽  
Exchange Processes ◽  
Outdoor Experiment ◽  
System Temperature ◽  
Experimental Trend ◽  
Experimental Approaches

This paper is aimed to investigate the heat transfer behaviours of a single slope solar still under the tropical climate at Kota Kinabalu city, Malaysia. Both theoretical and experimental approaches has been performed and discussed. The theoretical heat transfer principal behaviour of the single slope solar still is successfully modelled based on the heat exchange processes of three major components of the solar still (glass cover, seawater and basin) and its surroundings. The theoretical model developed has shown to predict closely the experimental trend of the heat transfer processes of the solar still system. Outdoor experiment is also carried out under the Kota Kinabalu, Sabah, climate that showed a maximum output of 1.4 litres per day of clean distilled water and has achieved a high and consistent system temperature of 80.0°C. In comparison with the theoretical and the experimental results, the theoretical model is found to closely predict the solar still behaviours at the early hours in the morning where the solar irradiance is intense and consistent.

Influence of fully submerged permanent magnets in the evaluation of heat transfer and performance analysis of single slope glass solar still

2021 ◽  
pp. 095765092110310
Author(s):  
Ajay Kumar Kaviti ◽  
Akkala Siva Ram ◽  
Amit Kumar Thakur
Keyword(s):  
Heat Transfer ◽  
Permanent Magnets ◽  
Outer Diameter ◽  
Solar Still ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Inner Diameter ◽  
Evaporative Heat Transfer ◽  
And Performance ◽  
Depth Water

In this experimental study, permanent magnets with three different sizes (M-1: 32 mm inner diameter, 70 mm outer diameter and 15 mm thick, M-2: 25 mm inner diameter, 60 mm outer diameter and 10 mm thick, M-3: 22 mm inner diameter, 45 mm outer diameter and 9 mm thick) are fully submerged in the single-slope glass solar still. The performance of magnetic solar stills (MSS) with three different sizes at 2 cm depth water to ensure that magnets are fully submerged is compared with conventional solar still (CSS) at the location 17.3850°N, 78.4867°E. Tiwari model is adapted to calculate the heat transfer coefficients (HTC), internal and exergy efficiencies. MSS with M-1, M-2 and M-3 significantly enhanced the convective, radiative, and evaporative heat transfer rate for the 2 cm depth of water. This is due to the desired magnetic treatment of water, which reduces the surface tension and increases the hydrogen bonds. The MSS's total internal HTC, instantaneous efficiencies led CSS by 25.52%, 28.8%, respectively, with M-1. Having various magnetic fields due to different magnets sizes increases MSS's exergetic efficiency by 33.61% with M-1, 33.76% with M-2, and 42.25% with M-3. Cumulative yield output for MSS with M-1, M-2, and M-3 is 21.66%, 17.64%, 15.78% higher than CSS. The use of permanent magnets of different sizes in the MSS is a viable, economical and straight forward technique to enhance productivity.

Fuel Spray Trajectory in Diesel Engines

1978 ◽  
Vol 100 (2) ◽  
pp. 326-332 ◽  
Author(s):  
M. M. Elkotb ◽  
N. M. Rafat
Keyword(s):  
Heat Transfer ◽  
Theoretical Model ◽  
Working Conditions ◽  
Fuel Spray ◽  
Air Velocity ◽  
Spray Penetration ◽  
Injection Angle ◽  
Velocity Pattern ◽  
Spray Volume ◽  
Spray Velocity

A detailed investigation of the effect of the shape of an open combustion chamber for diesel engine on the air velocity pattern, and consequently, on the trajectory of the fuel spray is given in this paper. A theoretical model for the calculation of the spray penetration, taking into consideration the heat transfer to the droplet, the variation of the drag force with Reynolds number, and air velocity pattern, is suggested. The effect of some working conditions on the spray shape, trajectory, and penetration is experimentally studied to verify the theoretical model and to correlate the results of using different medium pressures, initial spray velocity, and injection angle on the magnitude of fuel spray diameter and spray volume.

Calculation of Hourly Output of a Solar Still

1993 ◽  
Vol 115 (4) ◽  
pp. 231-236 ◽  
Author(s):  
V. B. Sharma ◽  
S. C. Mullick
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Heat Balance ◽  
Solar Still ◽  
Balance Equations ◽  
Transfer Coefficients ◽  
Heat Transfer Coefficients ◽  
Hourly Output ◽  
The Heat Balance

An approximate method for calculation of the hourly output of a solar still over a 24-hour cycle has been studied. The hourly performance of a solar still is predicted given the values of the insolation, ambient temperature, wind heat-transfer coefficient, water depth, and the heat-transfer coefficient through base and sides. The proposed method does not require graphical constructions and does not assume constant heat-transfer coefficients as in the previous methods. The possibility of using the values of the heat-transfer coefficients for the preceding time interval in the heat balance equations is examined. In fact, two variants of the basic method of calculation are examined. The hourly rate of evaporation is obtained. The results are compared to those obtained by numerical solution of the complete set of heat balance equations. The errors from the approximate method in prediction of the 24-hour output are within ±1.5 percent of the values from the numerical solution using the heat balance equations. The range of variables covered is 5 to 15 cms in water depth, 0 to 3 W/m2K in a heat-transfer coefficient through base and sides, and 5 to 40 W/m2K in a wind heat-transfer coefficient.

A Pulsed Wire Probe for the Measurement of Velocity and Flow Direction in Slowly Moving Air

1984 ◽  
Vol 106 (1) ◽  
pp. 72-78 ◽  
Author(s):  
D. E. Olson ◽  
K. H. Parker ◽  
B. Snyder
Keyword(s):  
Heat Transfer ◽  
Theoretical Model ◽  
Spatial Resolution ◽  
Flow Direction ◽  
Three Dimensional ◽  
Velocity Fields ◽  
Transport Time ◽  
Wire Probe ◽  
Circular Pipes ◽  
Measured Flow

This report describes the theory and operation of a pulsed-probe anemometer designed to measure steady three-dimensional velocity fields typical of pulmonary tracheo-bronchial airflows. Local velocities are determined by measuring the transport time and orientation of a thermal pulse initiated at an upstream wire and sensed at a downstream wire. The transport time is a reproducible function of velocity and the probe wire spacing, as verified by a theoretical model of convective heat transfer. When calibrated the anemometer yields measurements of velocity accurate to ±5 percent and resolves flow direction to within 1 deg at airspeeds ≥10 cm/s. Spatial resolution is ±0.5 mm. Measured flow patterns typical of curved circular pipes are included as examples of its application.

scholarly journals Investigation of Structural Stability for Monolithic Nano Bridges on Micro Apertures

2020 ◽  
Vol 10 (8) ◽  
pp. 2922
Author(s):  
Jinwon Lee ◽  
Changwook Seol ◽  
Le Vu Nam ◽  
Segeun Jang ◽  
Junsoo Kim ◽  
...  
Keyword(s):  
Theoretical Model ◽  
Structural Damage ◽  
Polymeric Membranes ◽  
Aperture Size ◽  
Stability Criteria ◽  
Design Rules ◽  
Thin Membranes ◽  
Experimental Approaches ◽  
The Stability ◽  
Line Patterns

The instability of polymeric membranes with nano- and micro-sized apertures has been regarded as one of the main reasons behind realizing ultra-thin membranes with apertures. As is well known, when the thickness of the membrane gets thinner or the aperture size gets smaller, the possibility of geometrical deformation or structural damage by collapse or fracture increases. Herein, we suggest the design rules for the stability of polymeric membranes possessing 1D nano-line patterns monolithically constructed on micro-aperture supporting layers. The proposed theoretical model, which has been thoroughly demonstrated and analyzed based on both theoretical and experimental approaches, provides stability criteria for lateral collapse and vertical fracture of ultra-thin membranes with apertures.

Boiling Heat Transfer With Binary Mixtures: Part I—A Theoretical Model for Pool Boiling

1998 ◽  
Vol 120 (2) ◽  
pp. 380-387 ◽  
Author(s):  
S. G. Kandlikar
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Theoretical Model ◽  
Transfer Coefficient ◽  
Binary Mixtures ◽  
Boiling Heat Transfer ◽  
Present Model ◽  
Pool Boiling ◽  
Interface Temperature ◽  
Pool Boiling Heat Transfer

Experimental evidence available in the literature indicates that the pool boiling heat transfer with binary mixtures is lower than the respective mole- or mass-fraction-averaged value. Although a few investigators have presented analytical work to model this phenomenon, empirical methods and correlations are used extensively. In the present work, a theoretical analysis is presented to estimate the mixture effects on heat transfer. The ideal heat transfer coefficient used currently in the literature to represent the pool boiling heat transfer in the absence of mass diffusion effects is based on empirical considerations, and has no theoretical basis. In the present work, a new pseudo-single component heat transfer coefficient is introduced to account for the mixture property effects more accurately. The liquid composition and the interface temperature at the interface of a growing bubble are predicted analytically and their effect on the heat transfer is estimated. The present model is compared with the theoretical model of Calus and Leonidopoulos (1974), and two empirical models, Calus and Rice (1972) and Fujita et al. (1996). The present model is able to predict the heat transfer coefficients and their trends in azeotrope forming mixtures (benzene/methanol, R-23/R-13 and R-22/R-12) as well as mixtures with widely varying boiling points (water/ethylene glycol and methanol/water).

Multiphysics for Early Stage Cement Hydration: Theoretical Framework

2011 ◽  
Vol 255-260 ◽  
pp. 4247-4250
Author(s):  
Zhen Liu ◽  
Bin Zhang ◽  
Xiong Bill Yu
Keyword(s):  
Heat Transfer ◽  
Energy Transfer ◽  
Theoretical Model ◽  
Numerical Model ◽  
Cement Hydration ◽  
Early Stage ◽  
Diffusion Theory ◽  
Equation System ◽  
Heat Transfer Theory ◽  
Reaction Theory

The chemical hydration involves complex multiphysical processes including mass and energy transfer, chemical reactions and consequently stress development and shrinkage. This paper proposed a multiphysics numerical model to predict the kinetics cement paste. The chemical reaction theory, heat transfer theory, diffusion theory, and continuum mechanics were coupled in the theoretical model. A comprehensive theoretical model is established with partial different equation system, auxiliary functions, and typical boundary conditions.

Mechanisms of Gas Turbine Regenerator Fouling

1967 ◽  
Author(s):  
James A. Miller
Keyword(s):  
Heat Transfer ◽  
Particulate Matter ◽  
Theoretical Model ◽  
Gas Turbine ◽  
Two Phase ◽  
Degradation Data ◽  
Proposed Model ◽  
Controlling Mechanism ◽  
Adhesive Coating ◽  
Phase Process

Possible mechanisms of gas turbine regenerator fouling are examined and compared with extant experimental evidence. A theoretical model of fouling which encompasses a two-phase process is proposed. It is shown that the controlling mechanism is the condensation of heavy hydrocarbon isomers which form an adhesive coating in which particulate matter subsequently become entrapped. Typical overall heat transfer and pressure drop degradation data are presented which tend to support the proposed model.

Statistical Determination of the Experimental Channels Clogging Rates in Mini- and Microchannel Heat Exchangers

2019 ◽  
Vol 142 (2) ◽  
Author(s):  
Witold Rybiński ◽  
Jarosław Mikielewicz
Keyword(s):  
Heat Transfer ◽  
Heat Exchanger ◽  
Theoretical Model ◽  
Pressure Drop ◽  
Cold Water ◽  
Nondestructive Method ◽  
Microchannel Heat Exchanger ◽  
Statistical Determination ◽  
Experimental Values

Abstract This paper presents a new statistical, nondestructive method for determination of the experimental channels clogging rate in a mini- or microchannel heat exchanger. Channels clogging may be caused by inaccurate fabrication of the heat exchanger or by fouling of microchannels during exploitation. The theoretical model, used in this method, predicts a significant increase of the pressure drop as the number of clogged microchannels increases. However, the exchanger’s heat transfer rate decreases moderately. It may partly be caused by the additional heat transfer in metal walls, bypassing the inactive, clogged microchannels. The presented method was tested on the prototype of a microchannel heat exchanger. The experimental values of the pressure drop of the hot and cold water flows are 2–5 times higher than the values predicted for clean microchannels. The experimental values for the pressure drop and heat transfer are in good agreement with the values calculated by the use of the theoretical model. The presented statistical method gives two channels clogging rates (for the “hot” and “cold” channels) obtained during normal exploitation without cutting (destroying) the heat exchanger.

Design and Simulation of a Novel Thermoelectric Micro-Device with Electrodeposited Bi-Te Alloys

2018 ◽  
Vol 281 ◽  
pp. 788-794
Author(s):  
S. Guo ◽  
Ning Su ◽  
Fu Li ◽  
Da Wei Liu ◽  
Bo Li
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Output Power ◽  
Short Circuit ◽  
Maximum Output Power ◽  
Convection Heat Transfer ◽  
Open Circuit ◽  
Maximum Output ◽  
Transfer Coefficients

A novel thermoelectric micro-device was designed with n-type and p-type Bi-Te materials alloys via a template electrodeposition process. The glass template including 250 holes in 10×10 mm2with a thickness of 200~ 400 µm. The diameter of the holes is 50~ 80 µm and the distance of adjacent centers of the holes is 200 µm. According to the design, the performance of heat transference and thermoelectric energy generation are simulated by COMSOL Multiphysics. In order to simplify model, there are 16 units in total, and each unit is made up of 16 (4 × 4) pillars. In the simulation, the largest temperature difference is 7.8K on the conditions of 500 W/m2K in convection heat transfer coefficients and the maximum output potential of the module is 21.7 mV. The maximum output power achieved 96.9 µW under 500 W/m2K of heat transfer coefficient and 10 mA of current. Under ideal conditions, the value of open circuit voltage and maximum output power increases to nine times as the model, but short circuit current remains the same. When the heat transfer coefficient is 500 W/m2K and the current density is 10 mA, the maximum output power of the actual product achieved 871.7 µW.

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