chiller purpose

[gabriel84]

i'm a student in hvac in college. i may sound stupid but i've been wondering, what is the purpose of having a chiller and sending cold water throughout a building? Why can't you have a system like an a/c just on a bigger scale with refrigerant circulating throughout the building?

[freonguy]

To start to answer your question -

- I guess you can liken it to a grocery store in a way - but in a '' food '' application, there is a 24/7 load - ie; a rack system with refrigerant pipes running to the evaporators with different loads / temperatures -- large systems with large refrigerant charges and lots of copper piping.

- In a chiller application, you can run the water through cheaper iron piping
- you don't have to worry about oil return considerations
- you can pump the water up many stories easily - long runs of refrigerant lines can lead to trouble and capacity losses
- varying loads are somewhat easier to control on a central chiller plant
- let some others add more ----

Some drawbacks to chillers -

- water management and proper treatment
- freezeup potential both in the chiller and on lines in the winter ( ie: glycol required )
- water pumps
- etc.

There will be some other great responses from out there as well. Good luck in school and good that you are asking questions.:rolleyes:

[txhvac]

They have exactly what your talking about out in some buildings, they're refered to as built-up DX (direct expansion). They are generally found in older buildings. Chilled h20 is more economical, less refrigerant is used, easier install, less leaks etc. h20 becomes your 2ndary refrigerant. Same thing all your trying to do is cool air.

[Chillpro]

Here is a simple reason:

R-22 $10.00/lb
H20 $.17/lb

It is more cost effective to run water lines than refrigerant lines.
less metering devices and possible down time.

The only increase is water treatment and pumps.

[maxster]

started up a contractors install years ago he had a 5 story school with york chillers in the basement they were air cooled split piped up to rooftop condensers.the total on each circuit was in the 275-300 lbs range X 4 circuit.if they had gone packaged chiller air cooled they would on been in the 60 lbs range per circuit and all the equipment on the roof just pipe the chilled water into the house.the size on a chiller air cooled is 3 to 4 X that of a water cooled the same tonnage.

[gabriel84]

so i completely understand the water vs. refrigerant cost is way cheaper and other concers like long runs and oil could lead to bigger problems.
i have one other question what do you mean by water cooled or air cooled chiller. obviously i understand one is coole by air and one water but what is the difference and what adv and/or disadv do each have?
sorry for the questions but i'm a newb in the field. just trying to understand more than just small time a/c.

[chiller rob]

using water cooled equipment you can generally count on lower head pressure with means the compressor doesnt have to do as much work to move the refrigerant thru the cycle... this is done usually via a cooling tower there are serveral different ways...

Air cooled is usually prefered if maint is a concern as any one can wash a coil periodically

the tower needs water treatment also or your heat exchangers can foul up....

once you get a grasp on some of the fundamentals... task your self to learn the different types of compressors that are used and see if YOU can reply back with as list....

[RcOKC]

Water cooled machines have a cooling tower and a pump to pump water thru condensor and up to cooling tower where it is cooled by ambient air by via a fan. Air cooled machines have a multiple number of fans that that are turned on and off depending on head psi, of course you always have some running regardless of ambient and or load. Water cooled machines work better in high heat and load conditions here in OK, the evaporative cooling from tower results in lower head psi, lower compression ratio thus lower cost to run the compressor. Air cooled machines on the other hand there disadvantage is when you are dealing with high ambient conditions, the higher the ambient temp is the higher the medium (the air) that cools the refrigerant is. Resulting in higher head psi and higher comp ratio so more energy used to overcome ambient temp. Though air cooled machines when sized correctly will work great. Hope i made some sense in that, even though I contradict myself in my own statement. :confused:

[gabriel84]

ok well i do now understand this chiller concept. refrigerant absorbs heat from the water to cool it down. the water flows through pipes and has their own "evaporators" in different areas in a building which air flows across and gives up its heat to the water. the cycle then starts again.
now the refrigerant which picked up the waters heat know has to get rid of its heat either by means of air or water. if it were to be by air it would be comparable to a condensing unit of an a/c system. a water cooled system would be the same but what would happen to the water cooling the refrigerant how does this water expel its heat to continue cooling the refrigerant.\?
I have done some research and found 5 types of compressors in chillers Reciprocating compression, scroll compression, screw-driven compression, and centrifugal compression. I have also been exposed to new technology called Turbocor by Danfoss which is from what i know the newest and best type of compressor going.

[snipe70e]

The water gives up its heat in the cooling tower. As air is passes through the water some of the water evaporates, changes state. The changing of state from liquid to vapor absorbs heat from the water, cooling it.

[AC-boy]

"the water flows through pipes and has their own "evaporators" in different areas in a building which air flows across and gives up its heat to the water."

GOOD, except the evaporators part, nothing is changing state in the chilled water coil, the water is in liquid form the whole time, just picking up heat and coming out warmer.

A chiller is just a refrigeration machine, with the evaporator removing heat from liquid, not air. Some have air cooled condensers, some have water cooled.

A water cooled chillers condenser works like a water source heat pumps condenser. Heat transfers from refrigerant to water, pumps circulate water to a cooling tower, cooling tower rejects heat to the air outside.

It's all about heat transfer.
No matter what, or how elaborate the setup, it's all about moving heat, saving energy, initial cost (unfortunately), what is possible and most practical in the building and space provided.

hot water may also be pumped thoughout the building, a hot water coil might be placed inline with the chilled water coil, a thermostat opens a hot water valve, or a chilled water valve with a call for heaing or cooling.

the air conditioner only moves heat, while the heater converts another form of energy to heat energy and then you must transfer it where it's needed.

[gabriel84]

does anyone know where i can find pictures of water towers for water cooled condensors, and pictures of chilled water coils?
i have seen many different things in the field but i'm trying to put everything together so it makes sense and i understand the where, how, and why things are.

[hvac_superman]

You will appreciate the chilled water system the first time you work on a split system and have to walk 5 miles thru the building then another 5 miles to the unit on the roof. That gets old in a hurry. With the chilled water you either have it or you don't.

[chiller rob]

thanks for getting back on the compressors, it shows that you are taking this seriously and just not asking questions without doing some leg work yourself...

the answers you are getting are great... there is some real talent on this site...

do a little more leg work on the cooling towers and chilled water coils... there is alot of imformation out there and with a little effort it can be had... just google...

just remember in the "moving heat" conversation if you can do it with a latent change you dont have to rely on sensible heat only...

we know from fundamentals that this is what we are doing on the primary side but that does not limit latent work on the secondary side also...

for example air cooled condenser will only cool the refrigerant with a sensible transfer on the air side so it may take a lot of air at high load to do the job

for water cooled condensers the warm water goes to the cooling tower and is put usually in the top were it falls over fill media toward the sump... air moves counter flow to that via a fan... what happens is not only do you get a sensible change of temperature to the water via the air but a part of the water will boil off releasing its latent heat load... this causes the drift "steam" comming out of the tower while it is in operation... the water collected in the sump is cool and pumped back to the chiller condenser to pick up heat again and continue the cycle...

it is good to see enthusiatic intest in this industry...

can you name some of the ways that we start 3 phase equipment electrically? i count 6 basic ways...

i will give you the first one, accoss the line contactor...

good luck

[skorepeo]

[quote=chiller rob;1661467]thanks for getting back on the compressors, it shows that you are taking this seriously and just not asking questions without doing some leg work yourself...

the answers you are getting are great... there is some real talent on this site...

do a little more leg work on the cooling towers and chilled water coils... there is alot of imformation out there and with a little effort it can be had... just google...

just remember in the "moving heat" conversation if you can do it with a latent change you dont have to rely on sensible heat only...

we know from fundamentals that this is what we are doing on the primary side but that does not limit latent work on the secondary side also...

for example air cooled condenser will only cool the refrigerant with a sensible transfer on the air side so it may take a lot of air at high load to do the job

for water cooled condensers the warm water goes to the cooling tower and is put usually in the top were it falls over fill media toward the sump... air moves counter flow to that via a fan... what happens is not only do you get a sensible change of temperature to the water via the air but a part of the water will boil off releasing its latent heat load... this causes the drift "steam" comming out of the tower while it is in operation... the water collected in the sump is cool and pumped back to the chiller condenser to pick up heat again and continue the cycle...

I had a newby ask me how this all worked he thought that the chilled water loop and the condenser water loop were the same.

LOL In his mind the water went through the towers then through the chiller then through the building air handlers back to the cooling towers!!! He could not grasp the idea that they were separate systems and one was sealed and one wasn't. Finally I used colored markers and a white board to have him visually see how it worked. The look of dumbfound to understanding was amazing when suddenly his mind grasped what he had been taught about thermodynamics!

Technically the water in the tower is boiling off the heat that it absorbed from the refrigerant in the condenser. And as we know when a liquid boils it evaporates and cools!!

somewhere I have real good info on the web but will have to find the address then I will post it

[skorepeo]

found one will get the other but this one is good

http://www.efftec.com/learning.html


this one is kinda long but diagrams of different applications in the middle are good

http://www.taylor-engineering.com/downloads/cooltools/CT-016_Design_Guide.pdf

[Shophound]

I had a newby ask me how this all worked he thought that the chilled water loop and the condenser water loop were the same.

LOL In his mind the water went through the towers then through the chiller then through the building air handlers back to the cooling towers!!! He could not grasp the idea that they were separate systems and one was sealed and one wasn't. Finally I used colored markers and a white board to have him visually see how it worked. The look of dumbfound to understanding was amazing when suddenly his mind grasped what he had been taught about thermodynamics!

Technically the water in the tower is boiling off the heat that it absorbed from the refrigerant in the condenser. And as we know when a liquid boils it evaporates and cools!!

somewhere I have real good info on the web but will have to find the address then I will post it

To say that water in a cooling tower is "boiling off" might seem a bit confusing to a newbie, who might confuse a cooling tower with a boiler. :D Technically, a portion of the water is changing state, from liquid to vapor, just as water does when most people think of the word "boil" (water to steam via a concentrated heat source). It is not incorrect to say that water "boils" inside a cooling tower...it just may take some folks a bit longer to wrap their head around the idea that water can "boil" at temperatures less than 212°F.

One thing to understand about cooling towers...they can only cool the water in them down to the wet bulb temperature of the ambient air entering the tower. Most towers under normal loads cannot cool the water to wet bulb temps...this difference is known as "cooling tower approach temperature"...the difference between the wet bulb temperature and the temperature of the water leaving the cooling tower after it has been cooled.

Understanding wet bulb temperature is important in evaluating tower performance; higher wet bulb temperatures result in less cooling effect due to evaporation, due to higher moisture content of the air entering the tower. While even in high wet bulb temperatures, a cooling tower will provide a better cooling medium for the chiller's condenser than an air cooled condenser can, the amount of heat rejection is reduced, resulting in a higher head pressure in the chiller's condenser barrel.

[habs]

Are you at St. Clair, who have you done your work experience with so far?There are a few guys from Windsor here.

[gabriel84]

i'm currently doing it with modern niagara

[gabriel84]

To say that water in a cooling tower is "boiling off" might seem a bit confusing to a newbie, who might confuse a cooling tower with a boiler. :D Technically, a portion of the water is changing state, from liquid to vapor, just as water does when most people think of the word "boil" (water to steam via a concentrated heat source). It is not incorrect to say that water "boils" inside a cooling tower...it just may take some folks a bit longer to wrap their head around the idea that water can "boil" at temperatures less than 212°F.

One thing to understand about cooling towers...they can only cool the water in them down to the wet bulb temperature of the ambient air entering the tower. Most towers under normal loads cannot cool the water to wet bulb temps...this difference is known as "cooling tower approach temperature"...the difference between the wet bulb temperature and the temperature of the water leaving the cooling tower after it has been cooled.

Understanding wet bulb temperature is important in evaluating tower performance; higher wet bulb temperatures result in less cooling effect due to evaporation, due to higher moisture content of the air entering the tower. While even in high wet bulb temperatures, a cooling tower will provide a better cooling medium for the chiller's condenser than an air cooled condenser can, the amount of heat rejection is reduced, resulting in a higher head pressure in the chiller's condenser barrel.

I understand exactly what you are saying about boiling. some of the water vapourizes which takes latent heat from the water to evaporate it. using the word boiling might confuse someone who doesn't know anything about the trade, but i do have a pretty good understanding of it. also it only makes sense the water in the cooling tower can only be cooled down to the wet bulb air temp, because the air cannot cool lower than that point. that would be impossible.
keep the info coming i think its making me smarter!!

[habs]

I figured you were with those guys given the turbocor experience. Good luck in school, when are you done?

[skorepeo]

Technically, a portion of the water is changing state, from liquid to vapor, just as water does when most people think of the word "boil" (water to steam via a concentrated heat source). It is not incorrect to say that water "boils" inside a cooling tower. water can "boil" at temperatures less than 212°F.

One thing to understand about cooling towers...they can only cool the water in them down to the wet bulb temperature of the ambient air entering the tower. Most towers under normal loads cannot cool the water to wet bulb temps...this difference is known as "cooling tower approach temperature"...the difference between the wet bulb temperature and the temperature of the water leaving the cooling tower after it has been cooled.

that is also logged and when plotted on a graph you can see tower efficiency

Understanding wet bulb temperature is important in evaluating tower performance; higher wet bulb temperatures result in less cooling effect due to evaporation, due to higher moisture content of the air entering the tower. While even in high wet bulb temperatures, a cooling tower will provide a better cooling medium for the chiller's condenser than an air cooled condenser can, the amount of heat rejection is reduced, resulting in a higher head pressure in the chiller's condenser barrel.[/quote]



I tried to explain that to my last boss but he did not get it told me that there was no reason to take wet bulb temp

I had a 600 ton flat plate heat exchanger that had not been used in over 10 years!! everyone said that it did not work! finally I got permission to try and fix it it took me 3 hours and I was able to use it so I shut down the chillers and shut down 2 cooling towers. that thing ran like a champion and saved a ton of money on electric cost. then they hired a new plant manager he just did not understand why I was logging all of these readings I said because if wet bulb gets above X and indoor temp is x and outdoor temp is x then we will have to change over to chillers. he couldn't understand why on one day at 74* F it would work and on other days at the same temp it wouldn't.

[gabriel84]

I figured you were with those guys given the turbocor experience. Good luck in school, when are you done?

hey who do you work for?

[timmy2734]

here's a couple of tower shots

http://i16.photobucket.com/albums/b11/TIMMY2734/tower.jpg

http://i16.photobucket.com/albums/b11/TIMMY2734/IMG_0178.jpg

http://i16.photobucket.com/albums/b11/TIMMY2734/IMG_0177.jpg

[maxster]

here is an air cooled rated at 400 tons if you had a 45-50 story office building you would need 10 of these to total 4000 tons of building load...where would your put them and all the related chiller pumps to the AHUs?http://img148.imageshack.us/img148/3212/rtaatranern8.jpg (http://imageshack.us)

[habs]

Justin will tell you who I am.

[maxster]

now talk water cooled and that tower shown is 600-800 tons right....and we said the building is 4000 tons load these would pipe into the tower from and adjacent penthouse room to them or down in a basement ant piped up.you wold need 5-800 ton tower sections(shown) and these chillers run up and thru 1250 tons each.so you go with 850 tons per unit you would install 4 @ 850 tons to total...3400 tons,and say a night chiller of 600 tons to make the 4000 tons design load.http://img141.imageshack.us/img141/6084/cvhegr6.jpg (http://imageshack.us)
the air cooled is 400 tons shown vs the water cooled shown at say 350-425 tons see how water cooled condensers are more efficant and sized to install in buildings.the chillers side wouldn't change in delivering the chilled water to the AHUs on each floor...pumps and contols would be standard but with different condensing systems.

[DPSwitch]

i'm a student in hvac in college. i may sound stupid but i've been wondering, what is the purpose of having a chiller and sending cold water throughout a building? Why can't you have a system like an a/c just on a bigger scale with refrigerant circulating throughout the building?

Cause you would need a bazillion pounts of freon.

[timmy2734]

It's used to cool 2 of these, each 400 ton screws

http://i16.photobucket.com/albums/b11/TIMMY2734/IMG_0107.jpg

[Shophound]

I tried to explain that to my last boss but he did not get it told me that there was no reason to take wet bulb temp

I had a 600 ton flat plate heat exchanger that had not been used in over 10 years!! everyone said that it did not work! finally I got permission to try and fix it it took me 3 hours and I was able to use it so I shut down the chillers and shut down 2 cooling towers. that thing ran like a champion and saved a ton of money on electric cost. then they hired a new plant manager he just did not understand why I was logging all of these readings I said because if wet bulb gets above X and indoor temp is x and outdoor temp is x then we will have to change over to chillers. he couldn't understand why on one day at 74* F it would work and on other days at the same temp it wouldn't.


In that case, your measuing and logging wet bulb temperatures was more critical than my own monitoring efforts...I just do it to see how well my towers are performing. You're doing it from a plant operation perspective, and whether or not to initialize "free cooling" via the towers that can, when conditons are favorable, shave off big dollars from operating costs. I don't have free cooling at my plant, but wish I did. The chillers run year round...I've considered other ideas like adding VFD to the chillers and maybe going to variable primary flow...but I'm not sold on those ideas just yet, whereas "free cooling" via a heat exchanger between tower and chilled water loop is pretty much a no brainer...when conditons are right.

Amazing to me in your case that such a thing can sit in the plant (representing an investment made by the owners of the plant) and not be used, AND not even understood by one charged with running the plant! It does no good to have whizbang amazing things in a central plant if nobody understands how to optimize those things. Might as well just run the chillers 24/7 with high kw/ton and low delta T.

[artman934]

i'm a student in hvac in college. i may sound stupid but i've been wondering, what is the purpose of having a chiller and sending cold water throughout a building? Why can't you have a system like an a/c just on a bigger scale with refrigerant circulating throughout the building?

easiest way i can some this up.

Chillers consist of the basic 4 components of an a/c system.

Now the difference is this. On a typical direct expansion unit, air passes over the evap coil, and the air is cooled because the coil absorbs the heat from the air. Now picture this, on a imagine water crosses that coil instead of air. You now have cold water(except this is done in a barrell and not over dx coil). The water is pumped to a series of air handlers in the space to cool the air in the space.

on the water cooled consenser, refrigerant goes from the compressor to the condenser of the unit (usually tube in shell), also called a barrell. heat from the gas is rejected to the water, the water is then pumped to cooling towers which cool the water, and the water is recirculated back to the condenser

thats it same basic stuff just some other goodies

[skorepeo]

In that case, your measuing and logging wet bulb temperatures was more critical than my own monitoring efforts...I just do it to see how well my towers are performing. You're doing it from a plant operation perspective, and whether or not to initialize "free cooling" via the towers that can, when conditons are favorable, shave off big dollars from operating costs. I don't have free cooling at my plant, but wish I did. The chillers run year round...I've considered other ideas like adding VFD to the chillers and maybe going to variable primary flow...but I'm not sold on those ideas just yet, whereas "free cooling" via a heat exchanger between tower and chilled water loop is pretty much a no brainer...when conditons are right.

Amazing to me in your case that such a thing can sit in the plant (representing an investment made by the owners of the plant) and not be used, AND not even understood by one charged with running the plant! It does no good to have whizbang amazing things in a central plant if nobody understands how to optimize those things. Might as well just run the chillers 24/7 with high kw/ton and low delta T.

Exactly what they were doing everything was controlled by a Trane tracer (old school) system set to automatic no one ever had to know anything but clean the towers. apparently the plate ran for 3 years then in 1995 they upgraded to a tracer 12.0 and a new 386 computer (still old schoool) tried to incorporate the plate into the program but it did not work the way that he set it up. The plant manager eventually quit and the replacement had no clue what to do. so it sat not used then after 2 years he quit and his replacement was told "never has worked right" finally they hired me low salary but one bonus was percent of money saved over previous years utility.

:DI fixed that plate lickity split saved and got bigger bonus $:D I made twice what my manager made:D