 నోనోలిని క౜మాల్లా నోత్ల్స్ట్ిందింపెత్తేయాపెన్ండింి త్రంన్్ంది ంవరనంశించిందాబర్పం్చించిమాశ్ట్యాటన్స్లెన్థణడి. ఇౚాల్ then we will see how to find the quantity of cooling water required in a condenser. the contents of this video session are first of all we will see how the vacuum in the condenser is measured then we will define the vacuum efficiency and write down the expression for the same then we will define the condenser efficiency and then the expression for condenser efficiency and then we will discuss how to find out the mass of cooling water required to condense one kg of steam now first of all let us see the vacuum measurement the vacuum as all of we know is pressure below atmospheric pressure or pressure less than atmospheric pressure this vacuum in the condenser is produced when the steam is condensed from vapor to liquid condition as the specific volume of liquid is much lower compared to the specific volume of dry or wet vapor and this vacuum in the condenser is usually measured in centimeters of mercury now let us pause the video for few seconds and let us think what are the various types of pressures and what is the relation between each type of pressure so first of all let us see what is atmospheric pressure atmospheric pressure is nothing but the pressure exerted by the atmosphere per unit surface area of the earth that is on the one meter square area of the earth and this pressure standard atmospheric pressure at mean sea level is 760 mmHg or 76 cmHg or it is also expressed in terms of bar as 1.01325 bar however this atmospheric pressure varies from location to location at standard mean sea level the standard atmospheric pressure is 1.01325 bar or 760 mmHg now let us see what is absolute pressure when the pressure is measured with reference to the perfect vacuum then it is called as the absolute pressure and third pressure which we call it as the gauge pressure is the pressure which is measured relative to the atmosphere now this gauge pressure can be more than atmospheric pressure or lower than atmospheric pressure when the gauge pressure is more than atmospheric pressure it is called as a positive gauge pressure when the gauge pressure is lower than atmospheric pressure it is called as negative gauge pressure or vacuum and the relation between these three pressures are absolute pressure equal to atmospheric pressure plus gauge pressure when the gauge pressure is more than atmospheric pressure वेरें, वें the gauge pressure is less than atmospheric pressure, the absolute pressure is given by the relation P absolute is equal to P atmospheric minus P gauge. Now let us see how actually the vacuum in the condenser can be measured. Now for that, for the reference, you can look at this figure. In this particular figure, we are having one container in which the mercury is filled. To measure the atmospheric pressure or barometric pressure, we are using one manometric tube which is filled with the mercury. And when this tube is inverted and put into this container, then at mean sea level, whatever pressure is exerted, this particular height will be equal to 760 mm of mercury. Or it is equal to 76 cm of mercury. And at the above this, as we can see, because this tube we have filled initially complete with the mercury, there is no air present. So this particular section is called as Toricillus vacuum or it is also called as perfect vacuum. So this tube, this device is called as a barometer and therefore this atmospheric pressure is also called as a barometric height or barometric pressure head. Now when we take the another manometric tube and one end of this tube is connected to the condenser shell and another section is connected to the vacuum head. As we can see, as we have already discussed, inside the condenser shell, the pressure is always a negative pressure that is a vacuum pressure. Therefore you can see that the pressure exerted, here it is the atmospheric pressure and this particular will be the vacuum pressure or negative gauge pressure. Therefore we can find the absolute pressure in the condenser will be given by the barometric height minus this particular vacuum gauge reading. And this vacuum gauge reading we can find using the vacuum gauge. So we will get the absolute pressure. This is how we can measure the vacuum inside the condenser. Now let us see the some terms related to performance of steam condenser. The first and very important term in case of steam condenser is the vacuum efficiency. Now the vacuum efficiency is defined as actual vacuum to the ideal vacuum. Ideal vacuum means maximum obtainable vacuum when air is absent, when the air is totally removed out of the condenser shell. Means only the steam will be there and it will exert its own partial pressure. This particular definition we can write in the equation form as vacuum efficiency will be equal to actual vacuum divided by ideal vacuum or maximum obtainable vacuum. And this particular actual vacuum as just now we have seen we can obtain an atmospheric pressure minus absolute pressure and the maximum obtainable vacuum or ideal vacuum. We can write it as barometric pressure minus absolute pressure of the steam. Here we will be taking the partial pressure of steam because there is no air is present. So in the equation form we can write the vacuum efficiency as Pb minus Pt upon Pb minus Ps where Pb is nothing but the atmospheric pressure or barometric pressure minus total pressure in the condenser. Where this pressure will be having will be summation of partial pressure of steam plus partial pressure of air. And in the denominator again the ideal vacuum will be written as barometric pressure minus here instead of Pt we are using Ps because air is absent. Here it will be only the partial pressure of steam that is absolute pressure of steam at the main condensing temperature. This is how we can find out the vacuum efficiency. Now let us see what exactly the vacuum efficiency tells us. The vacuum efficiency is the major of degree of perfection to maintain the desired vacuum in the condenser. Means suppose the vacuum efficiency is 90% we can say that we are maintaining almost 90% vacuum that is 90% vacuum compared to the ideal vacuum. So more the vacuum efficiency better will be the condenser, condensing effect. The vacuum efficiency mainly depends upon two parameters. First parameter is the effectiveness of air cooling. The air cooling if it is effective then the vacuum efficiency will be more because air can be removed very easily from the condenser shell and the rate at which air is removed by the air pump. It should be equal to the rate at which air is entering into the condenser shell. If we continuously remove the air through the condenser shell with the help of air pump at which it is entering then we will be able to maintain the desired vacuum in the condenser. So this is how the vacuum efficiency will give us the degree of perfection to maintain the desired vacuum in the condenser. Now let us see the another important parameter layer to condenser that is called as the condenser efficiency. Now condenser efficiency is defined as ratio of difference between outlet and inlet temperatures of cooling water. That we can say that rise in temperature of cooling water to the difference between temperature corresponding to the vacuum in the condenser and inlet temperature of the cooling water. That is nothing but the temperature of saturation temperature of cooling steam corresponding to the absolute pressure in the condenser. Now let us see how we can write the equation for condenser efficiency. So condenser efficiency can be written as actual rise in temperature of cooling water divided by maximum possible rise in temperature of cooling water. And we can write it as in equation form as tw2 minus tw1 upon ts minus tw1 where tw1 is the cooling water inlet temperature twt is the cooling water outlet temperature and ts is the saturation temperature corresponding to the absolute pressure in the condenser or we can also call it as mean condensing temperature. Now the last time one more important parameter which we call it as the cooling ratio. Cooling ratio is nothing but the ratio of mass of cooling water required per kg of steam to be condensed. This cooling ratio we can find out by writing a simple energy balance equation. That is as we know that in case of steam condenser the steam is condensed by giving the heat stream gate condenser by giving the heat to the cooling water. So we can write the energy balance equation as heat gained by cooling water equal to heat lost by the steam. And heat gained by cooling water we can write it as mcp delta d that is mass of cooling water into specific heat of cooling water into temperature rise of cooling water. That is tw2 minus tw1 which will be equal to heat lost by steam that is mass of steam into enthalpy of steam. Usually the steam is wet so we can write enthalpy of steam as hf plus x into hfd minus enthalpy of condenser which we can find from the steam table at the temperature of condenser. That is from temperature table at the temperature of condenser. So by using this equation we can write the equation for mw by mh that is cooling ratio mass of cooling water required to condense per kg of steam as h minus hc upon cpw into tw2 minus tw1. These are the references. Thank you.