[BLDG-SIM] How to stimulate displacement ventilation in eQuest?

[Rohini Brahme]

pretty much same as what I do except for the loads (lighting, people, and equipment) allocation to the plenum. 
It is very straighforward, if you have plenum zones. Just decide how much load goes to the plenum and input it under the equipment/light/people tab. You have to first assign a schedule so that the w/sqft numbers can be entered. For the people load, one thing to keep in mind is the outside air, if it is based on cfm/person. The plenum people do not get counted, so you will have to add extra cfm to the conditioned zone people.
 
- rohini
 
 

--------------------------------------------
Rohini Brahme, Ph.D.
Research Scientist
Energy & Building Solutions Group
Houston Advanced Research Center
4800 Research Forest Drive
The Woodlands, TX 77381

Ph: 281-364-6006
Fax: 281-364-6052



	-----Original Message-----
	From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of Renee J. Azerbegi
	Sent: Tuesday, August 29, 2006 8:31 PM
	To: BLDG-SIM at GARD.COM
	Subject: [BLDG-SIM] How to stimulate displacement ventilation in eQuest?
	
	

	Brandon,

	 

	Displacement ventilation. Always some what of a mystery......

	 

	This is a checklist I used for a recent project. I'd be curious to hear other's opinion on this subject.

System Type

Variable Air Volume 

Underfloor Distribution

Variable Air Volume         Overhead Distribution

TEMPERATURES

 

 

Supply air temp cooling

64 F from AHU

95 F from box heating coil

Supply air temp heating

67 F from box heating coil

55 F from AHU

ECONOMIZER

 

 

Economizer high limit

62 F 

53 F 

FANS

 

 

Supply/return fan static pressure 

0.9" ESP supply

0.6" ESP return

2.2" ESP supply

1.5" ESP return

LIGHTING

 

 

Light to conditioned space ratio

0%

100%

COOLING

 

 

Increase in cooling COP with higher supply air temp

10% increase in EER

9.8 EER

Reduced outside airflow due to higher ventilation effectiveness

20% reduction in outside air

Varies per air handling unit

	Notes:  

	1.	I could not find a place within eQuest to change the miscellaneous loads such that a portion of the load went to the plenum instead. 
	2.	I lowered the plenum height as much as possible but not to the 6 foot level as eQuest does not allow windows in the plenum zones. 
	3.	I used a VAV system, not a CV system as suggested below since there would be a heating coil with a damper to reduce the air flow at the zones. 

	 

	 

	Renée Azerbegi, CEM, LEED-AP

	ambient energy - solar & sustainable design solutions

	t 303.278.1532 | f 303.278.8533 | c 303.885.2695

	renee at ambient-e.com

	ambient-e.com  

	 

	
________________________________


	From: BLDG-SIM at GARD.COM [mailto:BLDG-SIM at GARD.COM] On Behalf Of Brandon Nichols
	Sent: Tuesday, August 29, 2006 5:12 PM
	To: BLDG-SIM at GARD.COM
	Subject: [BLDG-SIM] How to stimulate displacement ventilation in eQuest?

	 

	All,

	 

	Thanks for the responses on yesterday's question, 'simulating a VAV without cooling coil'.  A reasonable result was obtained by using a DX coil and setting the capacity to 1.  Believe I tried sending it to zero prior, but this as I now understand invoked autosizing.

	 

	Today I'd like to take a conventional VAV system with cooling and model its performance in a displacement ventilation (DV) configuration.  OUr 'typical school' DV does not require underfloor air distribution, so were not worried about accounting for any radiant effect.  I've read (well, skimmed) the Addison-Nall paper and they seem to explain the issues sufficiently, but didn't see anything in there I could explicitly apply to developing a DV model with eQuest.

	 

	Here is what Trane has to say about modeling displacement ventilation systems using Trace 700 (wherever they say 'underfloor' read 'displacement'):

	*	The air in a space supplied by an underfloor system is stratified and you only need enough airflow to handle the temperature (loads) in the lower stratified region. Trace (as well as the rest of the simulation programs) assumes well mixed spaces with the same temperature at all locations. 
	*	The way to handle this is to model the lower portion (the bottom 6 ft or so) as the height in the space. The top portion is then modeled by calling it a plenum space (plenum of about 5 or 6 feet). Then create custom miscellaneous loads and assign a portion of them to the plenum. The same thing can be done with the lights. 
	*	As for the system side, choose a Constant Volume Variable Temperature system. Go to the Temp/Humidity tab and assign a Leaving Cooling Coil Min and Max temperature of 55°F. Under the Direct/Indirect Humidification Controls, select "CV Mixed Air Bypass with Wild Coil Leaving Temp". 
	*	This will cause the temp off the coil to be low dewpoint, then air will be bypassed around main cooling coil and reintroduced and mixed back in after the main CC, which will allow the air to be supplied to the space with a reasonable %RH at a higher temperature (60-65°F). 

	When everything is working right, for equivalent space loads and equipment the DV model should allow a higher supply temperature (60-65°) and thus perform with measurably greater number hours of economizer operation than the conventional overhead distribution system.  

	 

	Does anyone have a similar checklist or reference to Trane's for doing a DV model in eQuest?  After having attended a one-day eQuest seminar, I am familiar with parameters.  But I'm not at all clear on how to assign say two thirds of the lighting load to a parameter, and transfer it to the exhaust air.

	 

	 

	 

	Thanks

	 

	Brandon Nichols, PE
	Mechanical
	HARGIS ENGINEERS
	600 Stewart St
	Suite 1000
	Seattle, WA 98101
	d | 206.436.0400 c | 206.228.8707
	o | 206.448.3376 f | 206.448.4450
	www.hargis.biz

	 

	
________________________________


	From: Brandon Nichols 
	Sent: Monday, August 28, 2006 5:15 PM
	To: 'bldg-sim at gard.com'
	Subject: How to simulate VAV systems without cooling coils in eQuest

	All,

	 

	 

	In the northwest USA we often use VAV systems without cooling for schools -- 100% outside air economizer cooling, and 'off' for three months in the summer.  The particular system I want to model in eQuest is the standard VAV with heat recovery, but I can't figure how to either define it without a cooling coil, or render the cooling coil and chiller ineffective.

	 

	What is the best way to do this?

	 

	 

	Thanks

	 

	Brandon Nichols, PE

	Mechanical

	HARGIS ENGINEERS

	600 Stewart Street

	Suite 1000

	Seattle, WA 98101

	www.hargis.biz

	 

	d | 206.436.0400  c | 206.228.8707

	o | 206.448.3376  f  | 206.448.4450

	 

	 

	 
	 
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