Technology progresses in the fields such as: electronic industries, high power engine and optical device that produce high heat flux is in a way that conventional methods are not able to remove the heat generated by these devices and need to advance cooling methods. There are two ways to improve the cooling processes. The first way is design of new cooling device with smaller channel dimensions that causes enhanced convective heat transfer coefficient due to increased fluid velocity [1, 2]. The use of microchannel as a cooling device for dissipating heat from silicon integrated circuit was first proposed by Tuckerman and Pease [3]. Two important goals in the electronics cooling are the reduction of maximum temperature of the device, and minimization of temperature gradients on the device surface that can be achieved by the use of microchannel heat sink (MCHS) [4]. The second way of enhancing cooling process is improving the heat transfer properties of fluids [5-9]. Since the thermal conductivity of metallic solids is much higher than the thermal conductivity of fluids, use of suspended millimeter or micrometer sized metallic solid particles in the fluid is expected to enhance the thermal conductivity of the base fluid [10]. To overcome the problems such as: abrasion, particles sedimentation, clogging, and finally additional pressure drop along the channel that occurs due to the large size of particles, the novel concept of nanofluid was first introduced by Choi and Eastman [11].Several experiments have been carried out to suspend various metal and metal oxide nanoparticles in several different base fluids by Choi and Eastman [7, 12-15].
Considering the importance of MCHS in the cooling processes, numerical and experimental stud...
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...r unless a surfactant used. Selvakumar and Suresh [22] experimentally measured the convective heat transfer coefficient of CuO/water nanofluid in the turbulent flow in an electronic heat sink. They found that the convective heat transfer coefficient of nanofluid increases with increasing flow rate and nanofluid concentration. Maximum increase in the convective heat transfer coefficient was about 29% which was occurred at 2 vol.% of nanofluid. They also proposed a correlation for Nusselt number in the turbulent flow regime in the microchannel.
In this study, local convective heat transfer coefficient and friction factor of CuO/water nanofluid in a rectangular MCHS were experimentally measured in the laminar flow regime. In these experiments, we focused on the effect of flow rate and nanofluid concentration on the heat transfer coefficient in the channel entrance.
Muller, S., Prowse, D. L., & Soper, M. E. (2012, September 25). CompTIA A+ Cert Guide: Power Supplies and System Cooling | Foundation Topics | Pearson IT Certification. Retrieved March 20, 2014, from http://www.pearsonitcertification.com/articles/article.aspx?p=1945640
Nano-thermal analysis methods are also known as micro-thermal procedures and they use the principle of characterizing highly localized materials on a micrometer. The characterization is then changed from a micrometer scale to a sub-micrometer scale with the temperature being regulated to the specified units. The application of nano-thermal analysis methods started towards the end of the 20th century. Although it has been applied in several other fields including microelectronics, its application in pharmaceuticals has not been that popular.
Convection is a transfer of internal energy into or out of an object by the physical movement of a surrounding fluid that transfers the internal energy along with its mass. According to Oxford Dictionary, convection is the movement caused within a fluid by the tendency of hotter and therefore less dense material to rise, and colder or denser material to sink under gravity's influence, that results in transfer of heat. Two fluids are liquid and gas.The fluid above a hot surface expands, becomes less dense, and rises.This applies to objects such as steam from a hot cup of coffee turning cool, ice melting like heat moving to ice from the air, or frozen material becoming raw like how frozen food thaws more quickly under cold running water. When
For the sample calculations, let’s use the marshmallow as an example. Its initial mass was 0.66 grams and its final mass was 0.36 grams. To calculate the amount burned, subtract 0.36 from 0.66 to get 0.30 grams. (Mass burned = mi- mf). To find the marshmallow’s change in temperature, use the formula (ΔT =
particles in it but not as much as the polystyrene cup so it will cool
After the water, has been boiling for 10 minutes, and the temperature inside the test tube has been stable for 5 minutes, record the temperature and remove the thermometer.
Sweating and Heat Loss Investigation Aim To find out whether heat is lost faster over a sweaty body compared to a dry body. Apparatus 2 Boiling tubes 47ml max 2 Measuring jug 50ml max A Beaker 250ml max 2 thermometers Paper towels A kettle to boil water A stopwatch 2 magnifying glasses (8x) 2 corks with a small hole through the centre A test tube rack Preliminary work In my preliminary work, I need to find out how much water to use, whether the tissue should be wet with hot/cold water, how often the readings should be taken, how accurate should the readings be, how many readings should be taken and what my starting temperature should be. My results are as follows. Starting temperature of 40°c Time (secs) Wet towel (°c) Dry towel (°c) 30 36 38.9 60 35 38.5 90 34 37.9 120 33.9 37.5 150 33 37 180 32.6 36.9 210 32.3 36.8 240 31 36.5 270 30.4 36 300 30.3 35.9 Starting temperature of 65°c Time (secs) Wet towel (°c) Dry towel (°c) 30 51.1 53 60 48.2 51.9 90 46.4 51 120 46 50 150 44.3 49 180 42.9 48.4 210 42.6 46.9 240 41.7 48 270 40.2 47.5 300 39.3 47 Starting temperature of 60°c Time (secs) Wet towel (°c) Dry towel (°c)
Conduction, Convection, and Radiation Heat transfer is the way heat moves through matter to change the temperature of other objects. There are three types of heat transfers, Conduction, Convection, and Radiation. The first kind of heat transfer, conduction, is heat transferring through direct contact of materials. This would be the same thing as a pan on the stove. The heat from the stove touches the pan directly, therefore making the pan hot.
- the effect of Viscosity on liquid flow (turbulent/laminar) I have consulted my teachers for guidance and I have also looked very carefully into the "the Suggestions papers" which contain many possible investigations which have been done in the past. I opted to choose neither of them but many aspects I will be looking into in my investigation are similar to those in the papers.
The process of conduction between a solid surface and a moving liquid or gas is called convection. The motion of the fluid may be natural or forced. If a liquid or gas is heated, its mass per unit volume generally decreases. If the liquid or gas is in a gravitational field, the hotter, lighter fluid rises while the colder, heavier fluid sinks. For example, when water in a pan is heated from below on my stove, the liquid closest to the bottom expands and its density decreases. The hot water as a result rises to the top and some of the cooler fluid descends toward the bottom, thus setting up a circulatory motion. This is also why the heating of a room by a radiator depends less on radiation than on natural convection currents, the hot air rising upward along the wall and cooler air coming back to the radiator from the side of the bottom. Because of the tendencies of hot air to rise and of cool air to sink, radiators are positioned near the floor and air-conditioning outlets near the ceiling for maximum efficiency.
As the pressure drop increases in the column, it is observed that the degree of foaming becomes more violent and more spread out. When the pressure drop is relatively high, it means that the pressure exerted by the vapour is insufficient to hold up the liquid in the tray, causing the gas bubbles to appear on top of the sieve trays. To add on, the higher the pressure drop, the higher the velocity of the vapour passing up the column. As a result, more vapour will penetrate the liquid and more bubbles formation is observed. Due to more bubbles formation, the degree of foaming are more agitated, rapid and spread out.
To investigate the temperature change in a displacement reaction between Copper Sulphate Solution and Zinc Powder
Temperature Changes During the Addition of Sulphuric Acid and Sodium Hydroxide Solution. Aim To investigate the temperature changes during the addition of sulphuric acid and sodium hydroxide solution. Introduction In this experiment we are using sodium hydroxide, sodium hydroxide. sulphuric acid.
When there is a change in the magnetic field near a material which is electrically conductive, there will be a current produced in the material know as eddy current. This eddy current is responsible for the heating of the material. The amount of eddy currents produced in the conductor depends mainly on the external magnetic field. Heat generation can be controlled by the magnetic field as the heat generated in the element is directly proportional to the current which depends on the magnetic flux. So heat is indirectly controlled by the magnetic flux.