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11 Dec 2014

Study and analysis of a cooling system for draught drinks

This is a brief review written by us of above mention article taken from sciencedirect.com 

Introduction


Draught drinks cooling system can be found in bars, restaurants and clubs etc which work 24 hours a day and 7 days a week. The basic draught drinks cooling system consist of two sub systems one is refrigeration subsystem and other is drink subsystem. The refrigeration subsystem consist of compressor, condenser, condenser fan, filter, expansion valve( capillary tube), internal heat exchanger and evaporator while drink subsystem consist of beverage coil,  column and tap. Other than this system has a tank having water in it. Evaporator and beverage coil both are also placed in the tank.




Working


During working evaporator absorb heat from water and drop its temperature to 0 degree C this water absorb heat from the beverage in beverage coil and drops its temperature to 3 degree C. Beverage in the column and tap is exposed to ambient temperature where its temperature can drop so to maintain a constant temperature water from the tank is circulated in the column and tap section with the help of a pump. In ideal working compressor work for 5 min and them switch of 23 min. In this 23 min ice in the tank melt and then in 5 min compressor restore it so the one cycle of refrigeration system is of 28 min. this can vary from on application to other like in small restaurant in peek consumption it is 30 min and in bars it is up to 73 min.






Experimental setup and Calculations

To measure the temperature and pressure, sensors are placed before and after the compressor, condenser, filter, expansion valve, internal heat exchanger and evaporator. When system start working we got the temperature and pressure readings and base on this information we made our calculation. When work done by compressor is known then we can find out mass flow rate and then with the help of the formula 
and steam table we can find the heat absorb or rejected by the condenser and expansion valve. Then with help of 2nd law of thermodynamic we can find the heat absorbed by the evaporator. Now we can find out the overall coefficient of performance of the refrigeration system.




In beverage cooling system there are three places from where ice can gain heat one is the outer atmosphere second is the beverage itself and the third is stirrer and pump installed inside the tank. Maximum heat absorb by the ice is when there is maximum consumption of beverage which depends upon the designing limitation of the machine. Power needed to cool down the beverage when there is maximum consumption is

Heat gain by the ice from the outer atmosphere came through lateral walls, bottom wall and top wall. Resistance given by each wall in heat flow is depending upon its thickness, area and thermal conductivity.


 Improvements needed

There are some improvements needed for this system like replacement of low efficient internal heat exchanger (having only 15% efficiency) by more efficient heat exchanger. System work 24 hours a day but when bar is closed there is consumption of energy for 5 min after every 23 min with no profit or beverage output solution is stop the machine when bar is closed but the problem is when bar is reopen system will take time to restore ice in tank. After experiments it is concluded that a real time clock must be integrated with the system so that sensor start the compressor time before the bar is open.


Conclusion

In this analysis of a cooling system designed for the cooling of the beverage drinks we have used pressure and temperature sensors and EES software for simulation and after many laboratory test we find that the COP of the refrigeration system was good about 3.14 but for the aver all system it was very low about 9.57E-2 which need to be improve. We have suggested the use of more efficient components as well as introducing a new real clock subsystem in the system to save energy.


8 Sep 2014

NESTLER BOILERS


Nestler boiler is a horizontal axis boiler and belongs from fire tube types of boilers. Shell of nestle boiler consist of two thick mild steel plates. A large number of fire tubes are fitted in between the steel plates.  A bigger diameter furnace tube extending from burner end to other end is used for carrying hot flue gases from one smoke box to the other smoke box. At the rear end smoke box chimney is provided for rejection of exhaust gases. Fuel which is used for the burning is a highely viscous fluid which is firstly heated up to 80 C and then supplied for the burning purpose. Nestler boiler can deliver the steam upto 10-11 bar pressure.


Parts of Nestler Boiler

  • Pressure gauge
  • Stop valve
  • Safety valve
  • Manhole
  • Chimney
  • Rear end smoke box
  • Centrifugal pump
  • Blow off cock
  • Flue tube
  • Burner
  • Front end sample box
  • Fusible plug


Working of Nestler Boiler


Fuel and high pressure air is mixed to produce the air fuel mixture which is burn in o produce the hot gases. Hot gases move through the furnace tube and enter the rear end smoke box of the nestler boiler. From the rear end smoke box hot gases enter into the fire tube which is surrounded by the liquid. Hot gases transfer their heat to the liquid and move forward into the front end sample smoke box from there finally hot gases moves toward the chimney from where they are eliminated into the atmosphere. Steam produce as the result of heat transfer between hot gases and water is collected into the steam chamber above.


6 Sep 2014

Locomotive boiler


They are the horizontal boiler and belong from the fire tube class of boilers. Locomotives boiler are divided into three main parts smoke box, shell box and fire box.


Parts of locomotive boilers

  • Grate
  • Damper
  • Ash pit
  • Fire box
  • Fire hole
  • Fire brick arch
  • Fusible plug
  • Operating rod
  • Steam whistle
  • Safety valve
  • Regulator
  • Barrel
  • Super heating tube
  • Steam pipe
  • Steam header
  • Smoke box
  • Blast pipe
  • Super heated steam out let
  • Chimney
  • Door



Working of locomotive boiler

Fuel is place on the grate where it is burned to produce the hot gases. Fire hole is used to feed the fuel. Hot gases which are produce as a result of fuel burning are diverted into fire tube with the help of fire brick arch. Steam produce is collected is the steam drum place at the top of the shell. As shown the wet steam goes through inlet headers of super heater and after passing through tubes, it returns to the outlet header of super heater and is taken out for steam engine. For the cleaning and maintenance of the complete boiler a door is provided at the side of the smoke box. Chimney is completely eliminated in locomotive boilers because they are always in motion


Application of locomotive boilers

Locomotive boilers are used to give power in following machinery
  • Steam railway engine
  • Marine steam engine
These boilers were invented for getting steam to run a steam engine used in locomotives.



26 Aug 2014

Cornish Boiler




Cornish boiler is a simple horizontal boiler which belong to the shell and tube class of boilers. Cornish boiler is much like the Lancashire boiler. Cornish boiler has the ability to produce steam at the rate of 1350 kg/hr and can take the maximum pressure of about 12 bar. Dimensions of the Cornish boiler shell is 4 m to 7 m in length and 1.2 m to 1.8 m in diameter. Cornish boiler is a fire tube type of boiler that is hot gases flow in tubes and water surround these tubes in shell.




Parts of Cornish boiler



Tubes

These are present inside the shell and hot gases flow through them.


Shell

A big shell which contain water inside it as well as tubes. Heat transfer between hot gases and water is take place here


Side flue

Flue are the tubes which take hot gases after they passes out from the fire tubes. Flue present at side of the horizontal shell are called side flues.


Bottom flue

Flue present at the bottom of the shell is called bottom flue. Bottom flue take the smoke toward the chimney.


Grate

Grate is the place where fuel is added for burning.


Ash pit

Ash pit the one which contain the ashes of fuel aster they are completely burn.


Chimney

Chimney take smoke from the bottom flue and take it out to the atmosphere.


Stop valve

It is used to regulate the flow of steam from boiler


Safety valve

Purpose of this valve is to stop the steam pressure from exceeding the maximum limit


Blow of cock

Blow of cock is used to clean boiler by discharging the water and sediments from bottom of boiler




Working of the Cornish boiler


Fuel is added in the grate area where it burn to produce hot gases. There hot gases move into the fire tube which take it inside the shell where it exchange its heat with surrounding water. Water take heat and after some time it start boiling to produce steam. Hot gases upon reaching at the end of the fire tube, divided into two section and each move into the one of two side flue which take them once again at the front section of the boiler where they are move into the bottom flue and bottom flue take them toward the chimney. Chimney throw these gases out of the boiler into the atmosphere. In this process hot gases travels complete length of boiler thrice that is once in fire tube then in side flue and at last bottom flue.  Maximum heat transfer is taken place at fire tube and shell section then taken place at side flue and at last at bottom flue.



Application of Cornish boiler


  • Cornish boiler are used in many industries like textile, sugar, paper, tyre, chemical etc

  • They are also used to produce steam to run steam turbine

  • They are also used in many marines


Advantages of Cornish boiler


  • Cornish boiler have simple design and easy construction

  • One of its main advantages is its Compactness and Portability

  • Low construction and maintenance cost

  • It has ability to overcome load fluctuation


 Disadvantages of Cornish boiler


  • Low steam production rate = 1350 kg/hr

  • Low maximum steam pressure range 12 bar

  • Need more ground because of horizontal structure