Tuesday, October 7, 2008

MICRO CHANNEL FLOW.

In micro channel flow the fluid passes through channels of hydraulic diameters in the order of millimeter.currently many people are working on this topic.The need for cooling solutions of small sizes is the main reason for the research in this particular area. Many people have been working on this area since 1980.
it was Tuckerman and pease(1980) who initiated experiments in this area and found deviations from conventional correlations. later WU and Little reported the same discrepancies followed by Choi Et Al ,Yu Et aL,Mala and Li etc.All the results so far quoted were based on experimental work.But in 2004, owahib came up with his experimental investigations that the heat transfer correlations were in accordance with the conventional ones.Then Lee and Garimella (2004) came with some ting new .They conducted NUMERICAL INVESTIGATIONS considering the effects of thermal boundary layers and all.Their numerical investigations were clearly in accordance with the conventional ones.Their work consisted of different cases ,they meticulously took into effect the of thermal and boundary layer . They conducted simulations for all the possible cases and came up with conclusion that the discrepancies which were found were because of the boundary layer effects.In the paper they have published various cases and in each case the numerical investigations were in accordance with the results which were in accordance with work earlier. LEE ,V.Garimella, Khandilekar are few of the people who are working extensively in this area.
To sum up, the micro channel flows and mini channel flows are in accordance with the conventional correlations .one has to be very careful in understanding the type of flow he is dealing with because in cases where flow is not completely developed the Nusselt number would be more than Expected .

3 comments:

Friday, September 12, 2008

How to LOCK a Folder without using any software in Windows XP

How to LOCK a Folder without using any software in Windows XP ...

*Copy the following codes (Marked in blue colour) :

cls
@ECHO OFF
title Folder Locker
if EXIST "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}" goto UNLOCK
if NOT EXIST Locker goto MDLOCKER
:CONFIRM
echo Are you sure u want to Lock the folder(Y/N)
set/p "cho=>"
if %cho%==Y goto LOCK
if %cho%==y goto LOCK
if %cho%==n goto END
if %cho%==N goto END
echo Invalid choice.
goto CONFIRM
:LOCK
ren Locker "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
attrib +h +s "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
echo Folder locked
goto End
:UNLOCK
echo Enter password to Unlock folder
set/p "pass=>"
if NOT %pass%==type your password here goto FAIL
attrib -h -s "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}"
ren "Control Panel.{21EC2020-3AEA-1069-A2DD-08002B30309D}" Locker
echo Folder Unlocked successfully
goto End
:FAIL
echo Invalid password
goto end
:MDLOCKER
md Locker
echo Locker created successfully
goto End
:End


* Now paste it in notepad.
* Change the "type your password here" with your password (Marked as bold in the above posted matter).
* Save it as batch file(with extension .bat).Any name will do.
* Now you see a batch file. Double click it to create a folder locker.
* A new folder named Locker would be formed at the same location.
* Now brings all the files you want to hide in the locker folder.
* Now double click the batch file to lock the folder namely Locker.
* If you want to unlock your files,double click the batch file again and you would be prompted for password.Enter the password and enjoy access to the folder.

Regards
http://allfree-stuff.com

0 comments:

Saturday, May 24, 2008

SHORTCUT KEYS : Run Commands To Access The Control Panel

SHORTCUT KEYS : Run Commands To Access The Control Panel

Add/Remove Programs control appwiz.cpl
Date/Time Properties control timedate.cpl
Display Properties control desk.cpl
FindFast control findfast.cpl
Fonts Folder control fonts
Internet Properties control inetcpl.cpl
Keyboard Properties control main.cpl keyboard
Mouse Properties control main.cpl
Multimedia Properties control mmsys.cpl
Network Properties control netcpl.cpl
Password Properties control password.cpl
Printers Folder control printers
Sound Properties control mmsys.cpl sounds
System Properties control sysdm.cpl

1 comments:

Tuesday, May 20, 2008

CRDe


CRDe stands for common rail diesel injection,one of the types of fuel injection. they allow for controlling injection timing ,injection pressure and injection quantity independently and decreases engine noise significantly.

Denso developed the first CRDe in 1995 and since then it has been supplying it to many companies. They are being used to meet the EURO 4 emission rules.

A high-pressure pump increases the fuel pressure in the accumulator up to 1,600 bar or 23,200 PSI. The pressure is set by the engine control unit and is independent of the engine speed and quantity of fuel being injected into any of the cylinders. The fuel is then transferred through rigid pipes to the fuel injectors, which inject the correct amount of fuel into the combustion chambers.

Injectors are actuated by electronic diesel control . some use piezo crystals .

The electronic diesel control unit precisely meters the amount of fuel injected, and improves atomization of the fuel by controlling the injector pulsations. This results in quieter, more fuel efficient engines; cleaner operation; and more power output.

1 comments:

Wednesday, February 20, 2008

scram jet design and oblique shock

In scram jets combustion occurs at super sonic air velocities. Oxygen is directly available from air and there is no need for tank to store oxygen. the velocities with which these engines run are very high about 10 -15 times sonic speed.

Intake of air matters a lot in this design . and it is a bit complex .

If the pressures with which air enter s the combustor increases we get high speeds .

In order to achieve high pressures the intake is designed in such a way to increase pressure. The main principle behind it being oblique shock occurrence which causes an increase in pressure and change in direction of flow .

The body of jet is provided with ramps (as shown in figure ) which are responsible for generation of oblique shock waves.the generation of oblique shock occurs at the tip of the ramp .the designing is done in such a way that the shock wave direction after meeting the ramp tips converge at the inlet of the intake of combustor and the flow is also directed towards the intake .

1 comments:

Thursday, February 14, 2008

FUEL INJECTORS



In trying to keep up with emissions and fuel efficiency laws, the fuel system used in modern cars has changed a lot over the years. For most of the existence of the internal combustion engine , the carburetor has been the device that supplied fuel to the engine. But as the automobile evolved, the carburetor got more and more complicated trying to handle all of the operating requirements.

At first, carburetors were replaced with throttle body fuel injection systems. Gradually, as new engines were designed, throttle body fuel injection was replaced by multi-port fuel injection.

Fuel-injection management comprises all the components which are involved in transferring the fuel from the tank and into the combustion chamber:

  • The low-pressure pump forces the fuel from the tank into the pressure chamber of the high-pressure pump.
  • The high-pressure pump compresses the fuel.
  • Mechanically or electronically triggered valves meter the correct amount of compressed fuel to the engine at the correct moment in time.
  • The fuel is then injected into the combustion chamber through the nozzles
Here is a over view of common rail injection systems being produced by bosch which gives us an idea about their progress

1997:
First Common Rail system in the world for passenger cars.
Injection pressure: 1,350 bar.

1999:
Common Rail system for trucks.
Injection pressure: 1,400 bar.

2001:
2nd generation Common Rail for passenger cars makes diesel engines even more economical, cleaner, quieter and more powerful. Injection pressure: 1,600 bar.

2002:
2nd generation Common Rail for trucks gives lower emissions, improved fuel consumption and more power.
Injection pressure: 1,600 bar.

2003:
3rd generation Common Rail with rapid-switch piezo inline injectors for cars.
Advantages: up to 20 % lower emissions or up to 5 % more power or up to 3 % lower fuel consumption or up to 3 dB(A) less engine noise.
Injection pressure: 1,600 bar.

2 comments:

Thursday, January 3, 2008

troubleshooting sound problems

Computers use sound cards to send sound signals from your computer to your speakers. A sound card is a piece of hardware inside the computer that can be built into the motherboard or a standalone card. These cards are usually PCI cards which is the most common add-on card type. There are companies who make external USB sound cards but they are not very common.
These sound cards use drivers to communicate with the operating system. For most users the operating system is some version of Microsoft Windows. Of course there are other operating systems such as Macintosh OSX and Linux. If the operating system doesn’t have the correct driver installed or no driver at all then it won’t know what to do with the new hardware and most of the time return some sort of error.

There are a few ways to install drivers for your sound card. The most common way is to install the driver/software from the CD that came with the sound card. Sometimes you will install the software before the card and sometimes you will install the card before the software depending on the manufactures instructions. The software contains the drivers and any other sound management utilities such as a mixer for example. Windows also has a way for you to manage your sound settings.
If you don’t have the CD that came with your sound card you can usually download it from the manufactures website if you know the model of the sound card. Another way to install drivers is from Windows update. This will only work if Windows recognizes your card and knows what drivers to look for. Sometimes if you restart your computer Windows will see that you have new hardware and ask you how you want to install the software for it. There will be a section asking you if you will allow Windows to go to search for drivers online and see if it can download the correct driver.
You can also go into Device Manager and find the sound card and double click it to open its properties. Then go to the Driver tab and click on update driver and follow the prompts to have it search your computer, CDROM or Windows update. If you don’t see your sound card look for an unknown device or an icon with a yellow question mark or exclamation point on it. This indicates that Windows sees the device but there is an issue with the driver. This is a good place to look if you are having sound problems with an existing sound card that came with your computer. The driver could have become corrupt or you may have inadvertently downloaded a new driver during Windows Update that is causing a conflict. There is a button to roll back the driver to go back to the previous version which may solve your problem. You can also remove the device from Device Manager, reboot the computer and let Windows detect the sound card again and reinstall the drivers.
If you are having problems with an existing sound card not working all of the sudden and everything looks fine in Device Manager then the next step is to check your speakers and speaker connection. If you have any other speakers or even an iPod or Walkman headset you can plug them in and see if you get sound. If so then your speakers are most likely not good anymore. Also make sure they are plugged into the right jack and that the plug is in all the way.
Next make sure your volume is turned up. Some speakers have separate volume controls on the speakers themselves that can be used in addition to the volume control within Windows. The speaker control is usually in the lower right corner by the clock and you can click on it to adjust the level. You can also double click on it to bring up other sound level controls.

If you don’t have the speaker icon by the clock then you can add it by going to Control Panel and then clicking on the Sounds and Audio Devices icon. From there check the box that says Place volume icon in the taskbar.
The next step is to check more of the options under Control Panel and the Sounds and Audio Devices section. Under the Volume tab you can check the volume, make sure it’s not on mute, and check the speaker volume and configuration. The Sounds tab allows you to configure what sounds play for what events in Windows. You can also turn off the Windows sounds if you don’t like them. It won’t affect your other sound settings. The Audio tab lists your sound device for playback, recording and MIDI music. Make sure the default device is what you have installed in your computer and not another device or older device that may have been removed. The Voice tab is similar to the Audio tab except its for voice playback and recording using some sort of microphone. The Hardware tab lists your installed audio devices including CD/DVD players. You can do basic troubleshooting from here as well as run the Sound Troubleshooter Wizard by highlighting the device and clicking on the Troubleshoot button. You can check the properties of the device as well as the driver configuration from the Properties button.
Another trick is to take the sound card out of its slot and put it a different slot if you have one available. If your sound card is built into the motherboard then this is not an option although you can add an actual sound card and use that instead of the built in sound card. You may want to go into the BIOS to disable the onboard sound card to avoid any conflicts. Finally it is possible that the sound card or speaker jack on the card has gone bad and you may end up having to replace it with a new one.

229 comments: