Direct Contact Heat Exchanger – Part 1





Hello friends, today we are going to start a very interesting type of heat exchangers very special type of heat exchanger they are called direct contact heat exchangers. So far the heat exchangers we have studied and discussed in this particular course where two fluids they do not they do not come into direct contact they exchange heat across a solid wall. On either side of the heat exchanger the solid wall there are 13 but I did suggest that there will be directing of the two mixing update weeklyobviously I did the special kind of idiots and yes the instructions are different hair design is different and applications are different so let us go to the next slide heat exchanger we can have service or indirect contact with exchanges and direct contact with excessive direct contact heat exchanger have got several advantages like high rate of heat transfer low temperature difference because the thermal resistance offered by the solid wall is no longer there be a temperature difference will be low and because again generally find that the tweet has not to pass through some sort of acorn do it the way we think that it has to pass through a fire particular passage Garfield bus is like that so narrow passage it has not to pass through a narrow passage so he will not will be a low air pressure drop then because we do not have a solid wall so all we do not have many solid walls has to be some sort of a containment structure should be there at those pictures are not there so we will have local housing maintenance advantages disadvantagesdisadvantages of contamination fluid mixing together for one minute that she has to be by decreasing the pressure the pressure of the other food then special arrangement to increase the surface area transfer the service out there andpalmistry or small bubbles etc to have a good amount of that directive streets are to be invisible should be two different phases of the solute like there is no problembetween alcohol and water we cannot mix them together because they are not amissah do they are visible through a mixture of alcohol and we also between them because that it will be very difficult it will be very difficult to separatesomebody contact with extended it should be liquid liquid heat exchanger condenser condensate there are different condenser slide condenser spring condenser back to call impact battery etc there was certainly different type of main direct direct contacta puppy that has been listed over here but men director direct contact with extensive list of different type of condensate conduit is there the cooling water it is coming like Egypt and from the turbines team is coming and the gate is made to pass through such a passage that some sort of a reform will be created and this team will be a course which team is coming at low pressure but even then he will be induced and YouTube is seduction up in there will be mixture of Steam and water will condense and ultimately there will be condensed and one can collect this contest so it has got a typical cell so this is like a convergent divergent and this is the divergent part or diffuser part of the nozzle to hear the liquid can be collected show the water is being sprayed so let’s say stamens coming from the top and water is being sprayed obviously this temperature should be lower than the steam temperature for that what we can do whatever is getting condensed weekday and the negative stranger mean we could father so that this is cool are compared to the outlet temperature of the condenser and it comes here and we get directions there could bePierre water is falling and steam is moving up so when this time is passing through the water like this and we will have the condensation there will be many trees like this so ultimately only non-condensable gas will be there between the top two things are very important in case of direct contact with extra mixing so that there is a very intimate contact between the two weeks and a good recipes presidents time obviously there is a date we have got two small droplets a large amount of surface area good mixing etc and what we can have after this we can have different obstacles to that the flu is not in a straight path so a good amount of time we both the liquid and the gas will be in contact so that we can have him see the gas is passing like this then these days is in this there is a z-pack and residents time is more and water is meant to fall in thin-film solar at the surface area is also that this is one thing we had to do to have a good fit exchange between the between the two weeks should do fluids you see tweets could be too very miscible liquids very very immiscible liquids which can be separated easily one thing could be there that if two liquids are having large density difference when girls another liquid and liquid liquidnow what we are having here is coming in and then it is passing through some sort of work and here we are spraying water in there so it was and then the worst year is passed through water droplet will be taken separately and then it will go to the help of and then we can get different here at different temperature and humidity in the conditions and controlling the humidity and the humidity of the air temperature has to be controlled via and another high school tower chili pepper water contact contact of ambient air with water and in both of them evaporation is a very important parameter of course other than evaporation something else could be there now and and we are having something called voice hear let me hear with water vapour we are getting it is very important to know the physics of air and water vapour and that is called psychometrics in the next life we will see very quickly recapitulate cyclamate the class of thermodynamics or refrigeration air conditioning I will not go into details but I will tell you something psychrometric chart looks like this this is a psychrometric chart that which gives the properties of moist air and it gives this these properties of moist air at a particular pressure and is commonly used psychrometric chart are for atmospheric pressure in this psychrometric chart tribal temperature varies in this direction ok loadable temperature high drive-in directions specific humidity is specific humidity in by the small wskg of water park city of Troy ok and it is proportional to water vapour pressure also show sometimes called kamdebo temperature in this direction we will get the moisture content from here ok and in this direction we will get the weight of the very small angle between them so that also can be obtained from then volumeand already pressure is constant show at one point I will reach the hundred percent related humidity or circulation cause this is called the dew point temperature this is the dew point temperature now if I put more humidity but I try to keep it so I will get the constant weight belt line and this way also I can reach the hundred percent saturation show me the nickname things regarding cyclic picture psychrometric processes we can see in the other diagram and most of these processes can be realised with the help of her ear was hurting and dehumidification which is to be spread in which is to be spread in a hair was so we can get many of these psychrometric processes I will not elaborate only one kind of heat exchanger I will spend some time because that is very important and only one type of direct contact it is danger I’d like to give some details because of the constant of time that is cooling tower so with this we will end our discussion on WhatsApp dislike thiswater makeup from a very large power plant fossil fuel power plant or nuclear power plant or it may come from a chemical plant or it may come from awesome awesomeI see that of the cooling towers like this okay I have phone we what we what we will have is like this there will be somewhere hot water will be injected water spray system here hot water will be some sort of elements to transfer element which is called me and this winter has got a chimney like structures that will create some sort of a natural draught by which a military pass through like this so hot water is falling lightness and MBA t-series passing in the from the lower side to the higher upside in the opposite direction so it is the counter-current flow kind of animal and we will have good amount of mixing and the hot waterB2B dry yet and buy that way it will get food so that is the way the water we get cold cold water will be collected at the bottom that can be taken again for tickets there is some sort of a ripped eliminated we can see some sort of drift eliminated is there because as the hot water is fasting in the downward direction where is passing in the opposite direction there will be small droplet of water will buy the ticket by the year that has to be separated so the eliminator we separate that way to sort of classification of cooling tower according to draught it could be either we have gotten all we have is called the mechanical clock and it could be used for reducing then it is if it is venable we have gotten in or we have got a fun with his called atmospheric cooling towers then mechanical drop cooling tower it will have and I know it could be new slot or it could be. If it is inducing airflow to the cooling tower then it is induced draught if it is forcing airflow to the cooling towers then it is for stuff that we can have some sort of the chimney that is creating the accurate it is called a natural rubber and there could be mixed with our unique design fire there will be natural plastic and according to theexplain it due to this chimney there is no fan of the year will be drawn and this could be very large structure and you see this is kind of a convergent divergent structure it has nothing to do with the nothing to do with the afro but this kind of structure gives greater stability to the cooling towers so this is actually from the structural design this is not from the fluid flow or heat transfer point of view that we have to give a convergent divergent kind of design this is some sort of a cross-flow side this is counterflow eat exchanges sorry counter flow cooling tower mechanical draught and induced drug-induced there is no fun so there is a fun so it will induce the airflow through the winter and there are in truworths year will come in and there is a sand should be fun in inducing the floor water is falling in the downward direction and their counterflow induced draught put out this is a club so you will be ok and there should be at the shop we can find this is your gift eliminator now this is a cash flow kind of cooling tower the diagram is not very well representative of very very very good representative because we will probably bewhat are we falling in the downward direction and year will be moving in the opposite direction to this is counter-current flow as we have gotten other heat exchanger also actually this is a mixed flow kind of cooling tower we can have some cooling tower or we can have some sort of a mixed flow that some flu is taking place like this and here also some flu is taking place they’re not very common design but in some cases we can have mixed look kind of cute overalls differentthis is without a fee atmospheric cooling tower in many cases we can find this atmospheric cooling tower they are generally small and with small refrigeration or air conditioning unit we can have this is a cross-flow it extends across flow cooling tower as I have told the wall should be slideshow Wallace length hair is moving like this and water is falling like this so it is a contraflow cooling tower site cross-flow cooling tower and here we have got thinking I think I have to explain what is Phil please and here we have got splashed feel so this is also I will explain should let me go to the 15 things like this let’s say we have got a like this so this is your feeling ok and fluffy so this is field and blessing is like this that we have got element in the path of air and water show water droplet is falling it is breaking into to draw plaits and load calculations and surely there is breaking into more block lettering and here it is falling like this morning like this from here it is falling and and and this is the difference between splash Shield and thinking now now things are very important in case of Quinta what one is range it is the temperature difference between the hot water entering the cooling tower and The coldwater leaving the range is virtually identical with the contents arise that means what is the temperature like in the condenser then there is another thing that is your approach the difference between the temperature of the water leaving the tower and Nick wet bulb temperature of the entering this is very important this this point I like to stress upon that in a cooling tower water temperature ideally should not dealing with don’t be the drywall temperature of the water it could be even lower than that that is the wet-bulb temperature of water for this a smallair condition this is the ebt of the ambient air condition dry bulb temperature in this is the wet-bulb temperature of the year that means is less than or equal towhat temperature could be even lower than the driver temperature but it will not be going to the difference between the wet-bulb temperature and the cold water temperature at Lake water temperature is denoted by cold water temperature is denoted by u o c w t o c w t minus wbz it is approaching the way. So with this I will, I would like to stop over here and then we will see some more aspects of cooling tower in our next lecture. Thank you