[Bldg-sim] Radiant slab Heating Cooling

[Pegues, James F CCS]

Varun,

 

You can use the workaround you mentioned for modeling radiant cooling and heating, and at the same time model the effects of your supply water temperatures for the chiller and boiler plants.  There is no conflict in HAP for doing both.  However, as Peter and others point out, you may need the chillers to operate with a cold LCHWT like 42 F anyway to serve your DOAS which is handling the full dehumidification load for your building and other chilled water consumers like AHUs if they exist. 

 

As part of your software license you have free access to HAP software support at software.systems at carrier.utc.com.  The support desk is staffed by engineers with decades of experience in HVAC design and application engineering, who are also experts in the software.  They can help you sort out these kinds of issues to determine which features of the software are best to use for your application.

 

Best Regards,

 

Jim Pegues

Carrier

 

From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of varun kulkarni
Sent: Friday, February 24, 2012 8:15 AM
To: Hisham Ahmad
Cc: bldg-sim at lists.onebuilding.org
Subject: Re: [Bldg-sim] Radiant slab Heating Cooling

 

All,

Radiant heating/cooling does not address the latent load. So if you have a space/building served by radiant heating/cooling, you have to have a ventilation unit (which might supply neutral air). This considerably gives a huge amount of saving when coupled with DCV.

Another point point is that a chiller with 55F LWT and boiler with 100F LWT would use less energy than conventional chiler/boiler LWT range. So, as Amit said, a de-coupler is needed (may be a heat exchanger) for chilled water and heating water to tie into other equipments in the building such as snowmelt, air handlers..

By the ratio of radiant floor and conditioned floor output, do you mean the ratio of energy consumed if the building was conditioned with either of the two approach?

On Fri, Feb 24, 2012 at 12:00 AM, Hisham Ahmad <hisham at edsglobal.com> wrote:

Hi Varun 

 

As a work around in DOE2. You may model the actual design temperatures and increase/decrease the indoor set points for cooling/heating by some margin.

 

Regards
Hisham Ahmad

Energy Analyst
Environmental Design Solutions Pvt Ltd.
www.edsglobal.com <http://www.edsglobal.com/> 
New Delhi, India
+91-9873065488 <tel:%2B91-9873065488> 



On 24 February 2012 09:38, Peter Simmonds <peter.simmonds at ibece.net> wrote:

	Varun, you might want to graduate from the HAP program. Unless you have two chillers one for 42F water and another for 55F, then most systems produce 42F water and then blend to 55F, so the potential savings are difficult to obtain. By the way what is the ratio of your radiant floor to conditioned air output?

	 

	Peter Simmonds, Ph.D., ASHRAE Fellow and DL

	Head of the Advanced Technology Group,

	IBE Consulting Engineers,

	14130 Riverside drive, suite 201

	Sherman Oaks, CA 91423

	Tel; 818-305-3246

	Mobile: 818-2191284

	 

	From: varun kulkarni [mailto:seldomvarun at gmail.com] 
	Sent: Thursday, February 23, 2012 11:05 AM

	
	To: Peter Simmonds
	Cc: bldg-sim at lists.onebuilding.org

	Subject: Re: [Bldg-sim] Radiant slab Heating Cooling 

	 

	Thanks Peter,

	 

	I am using Carrier HAP and when I model a fan coil unit, I am asked to input the design supply temperatures for heating and cooling (which is usually 95F and 55F). Now, i think these are going to drive my energy consumed at the boiler and chiller. The whole point (not the only point but a major though) of using radiant slab heating and cooling is lower temps for heating, higher temps for cooling and also the fact that water has higher energy carrying capacity then air. So if you are not able to take credit for that in modeling then obviously, the energy consumption number is not right. Thats my reason to segregate the different temperatures.

	On Thu, Feb 23, 2012 at 11:38 AM, Peter Simmonds <peter.simmonds at ibece.net> wrote:

	Varun, your perception is nearly true, but it depends on what you are modeling? If you are modeling the energy performance of a building a four pipe fan coil works just fine as it maintains the required energy balance. It is true that the actual performance of a radiant floor is different than a fan coil, but you are looking at energy and not optimal modeling.

	Your thoughts on stratification are somewhat correct. I would tend to think that stratification is caused by space heat load and air movement, especially displacement. Yes, there is a convective flow from the floor but this is quite small as the temperature difference between the floor surface temperature and the space operating temperature.

	Regarding temperature; this depends on what program you are using and why you want to segregate the different temperatures?

	 

	Peter Simmonds, Ph.D. 
	Senior Associate
	Head of the Advanced Technology Group
	IBE Consulting Engineers
	14130 Riverside Drive, Suite 201
	Sherman Oaks, CA 91423 
	d: (818) 305-3246 <tel:%28818%29%20305-3246>  o: (818) 377-8220 <tel:%28818%29%20377-8220>  f: (818) 377-8230 <tel:%28818%29%20377-8230> 
	
	www.ibece.com <http://www.ibece.com/> 
	Ideas for the built environment

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	From: bldg-sim-bounces at lists.onebuilding.org [mailto:bldg-sim-bounces at lists.onebuilding.org] On Behalf Of varun kulkarni
	Sent: Thursday, February 23, 2012 5:34 AM
	To: bldg-sim at lists.onebuilding.org
	Subject: [Bldg-sim] Radiant slab Heating Cooling

	 

	Good Morning everyone,

	 

	I have been reading through the archives for modeling radiant slab heating and cooling.

	Most popular and the closest to real world approach I found was using a 4 pipe fan coil unit and making the fan energy zero.

	I still have following questions:

	·         Did anyone think of using a factor, which when multiplied to the energy usage by fan coil system, give us the actual energy usage by radiant system. (I would guess it would be <1)

	·         As radiant heating and cooling forms a stratification layer in the space. And  we care about first 6-8 feet to be within desired temperature range. So to take that into account while modeling “it”  as fan coil unit, can we lower the ceiling height. Does that mean the conduction load from ceiling/roof or the wall above 6-8 feet doesn’t count ?

	·         The temperature range for heating water (95F-105F) and cooling water (55F-65F) pumped in the radiant system is different from the typical chilled water (44F-45F) and heating water (170F-180F). How do we make sure our model reflects this while using fan coil unit.

	 

	I am sure there are more questions you would have come across but these were some of my major concerns and I would appreciate any inputs/ suggestions.

	PS: This is a aspiring LEED platinum building.

	
	
	-- 

	Thanks and Best Regards,

	 

	 

	 

	Sincerely,

	 

	Varun Kulkarni 

	 

	Note: Please do not print, unless required.

	 

	 

	 

	
	
	
	-- 

	Thanks and Best Regards,

	 

	 

	 

	Sincerely,

	 

	Varun Kulkarni 

	 

	Note: Please do not print, unless required.

	 

	 

	 

	 

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-- 

Thanks and Best Regards,

 

 

 

Sincerely,

 

Varun Kulkarni 

 

Note: Please do not print, unless required.

 

 

 

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