Flow control in microfluidics devices: electro-osmotic Couette flow with joule heating effect

Purpose – Joule heating effect is a pervasive phenomenon in electro-osmotic flow because of the applied electric field and fluid electrical resistivity across the microchannels. Its effect in electro-osmotic flow field is an important mechanism to control the flow inside the microchannels and it includes numerous applications. Design/methodology/approach – This research article details the numerical investigation on alterations in the profile of stream wise velocity of simple Couette-electroosmotic flow and pressure driven electro-osmotic Couette flow by the dynamic viscosity variations happened due to the Joule heating effect throughout the dielectric fluid usually observed in various microfluidic devices. Findings – The advantages of the Joule heating effect are not only to control the velocity in microchannels but also to act as an active method to enhance the mixing efficiency. The results of numerical investigations reveal that the thermal field due to Joule heating effect causes considerable variation of dynamic viscosity across the microchannel to initiate a shear flow when EDL (Electrical Double Layer) thickness is increased and is being varied across the channel. Originality/value – This research work suggest how joule heating can be used as en effective mechanism for flow control in microfluidic devices

Investigation of dual–pass inclined oscillating bed solar dryer for drying of non-parboiled paddy grains

This Paper determines an experimental study of a dual-pass solar dryer with a bed tilt of 0.5° and varying the oscillating frequency of the drying chamber namely 1.25, 1.75, and 2.25 Hz for drying an agricultural produce namely non–parboiled paddy grains. The oscillations and bed tilt are provided to move the grains from entry to exit of the top bed and move down to the bottom bed and finally exit from the dryer. The new technology has been used in the solar dryer for drying agricultural produce as non–parboiled paddy grains to increase the quality and decrease the loss of the dried produce. The present dryer model was used for drying 45 kg of non–parboiled paddy grains from 19% (w.b) to the approved range of 12–14% of moisture content obtained in a single experimental day. The dried paddy grains obtained an average moisture content are 13.03, 13.22, and 13.51% at the frequency of oscillation of 1.25, 1.75, and 2.25 Hz, respectively. The maximum thermal and pick-up efficiency of the model was obtained at 1.00 p.m. in all cases. For the frequency of oscillation of 1.25, 1.75, and 2.25 Hz, the maximum dryer thermal efficiency was 44.47, 43.39, and 41.39%, respectively, and the maximum pick–up efficiency was 80.41, 79.19, and 76.21%, respectively. The optimum drying performance was obtained at the oscillating frequency of 1.75 Hz with the bed tilt of 0.5

Control of base flows with micro jet for area ratio of 6.25

Suddenly expanded flow with active controls in the form of micro jets has been investigated experimentally, laying emphasis on the effectiveness of micro jets on the base pressure and enlarged duct pressure field. Air injection at four locations at the base, symmetric to the nozzle axis is used as the active control. The jet Mach numbers of the present studies are 1.87, 2.2 and 2.58. The area ratio of present study is 6.25. The length-to-diameter ratio of the suddenly expanded duct and the Nozzle Pressure Ratio (NPR) are varied from 10 to 1 and 3 to 11. In addition to base pressure, wall pressure field along the duct was also studied. It is found that the active control in the form of blowing through small orifices (micro jets) are effective in controlling the base pressure field. Micro jets do not augment the flow field in the duct. As high as 55 percent, increase in base pressure was achieved for certain combination of parameters of the present study

Hydrocarbons as alternative refrigerants in domestic refrigerators

The thermodynamic and volumetric properties of hydrocarbons namely Propane, Cyclopropane, Propene, Methyl acetylene, Propadiene and Dimethyl ether as replacements to substitute R134a have been assessed by means of SRK equation of state. The pressure magnitude, enthalpy, entropy, and specific capacity at the vapor and fluid phase have been analyzed over the temperature range from -250C to +55 0C. Ten state point vapor compression cycle is used to carry out the thermodynamic investigation of 89W local refrigerator. The theoretical enactment of the hydrocarbons has been comparatively assessed using standard refrigeration parameters such as displacement volume, volumetric efficiency, starting torque, refrigerating effect, discharge temperature, COP and rating of the motor. According to our results, Propane and Propene are appropriate and recommended as alternatives of R134a with lower displacement compressor and Cyclopropane as a direct substitute. Also implications with respect to material and lubricant oil compatibility, heat transfer characteristics are discussed

Manufacturing and experimental characterization of new-developed natural fiber reinforced polymer nanocomposite

In this work, a nanocomposite polymer is developed using less utilised palm leaf stalk fiber as natural reinforcement and nano coconut shell powder blended with polyester resin as a matrix. The fibers are extracted from palm leaves. The fibers are treated with 5% potassium permanganate (KMnO4) as an alkali for 1 h. They are then thoroughly cleaned with water and dried in an oven. The fibers are chopped into short strands. The polyester matrix is pre-prepared by blending with coconut shell nanopowder. The fabrication of the composite is completed using these mats as reinforcement in the prepared blend. Mechanical tests are performed on the newly developed composites. The experimental findings are compared to similar natural fibers, and found that palm-based composite exhibits superior values. Structural electron microscopy observations reveal the presence of matrix, reinforcement and the absence of voids due to the addition of nanopowder. The developed composite may be recommended for automobile and aerospace applications