Hello my first post, 

I'm wondering if there is anyone about who could advise on the calculations involved in determining flow networks for natural ventilation. I'm studying a distance learning masters in sustainable design and there is something for this assignment I'm just not getting. 

I've been through 

A Guide to Energy Efficient Ventilation, Martin W Liddament – AVIC

Air Infiltration Calculation Techniques - An Applications Guide, Martin W. Liddament – AVIC

2009 ASHRAE® Handbook Fundamentals

Ventilation for Acceptable Indoor Air Quality, ASHRAEE standard 62.1

And several other presentations, book and publications.

and in part of this I found a couple of Discussions here that have helped but not fully covered what I need. 


If anyone can help I'll go into more detail but the basic layout is below. Obviously I don't want to solution calculated for me as that would be cheating but just people to bounce off would be nice. 

Views: 132

Reply to This

Replies to This Discussion

Pascals for stack has been discussed to death here

Wind is pretty easy to find & if need be I would recommend googleing Bernoulli's principle on wind

Unfortunately just looking at the diagram without some context it is hard to know what you need help with

https://www.linkedin.com/groups/6942179/6942179-6030115404729307139           'm not sure this is what your exactly looking for Daniel but it should direct you to the right area.

I asked this question to Colin Genge really one of best minds regarding this in the business. Anyone can theorize but measuring is why most of us are here. If your going to measure one thing against another do it the same way every time. This escapes some in our industry...Anyway take the time to read what he wrote on set-up and join his group. Best of luck and share what you come up with.             

Daniel,

I'm assuming you're trying to predict the airflows through the different openings W1, ... ? It is very unclear from the drawing. You're probably aware, but solving the problem requires calculating the pressure differentials at each opening, as they vary with height and temperature difference. The airflow is then simplified as an orifice flow, typically with flow and pressure coefficients that characterize the size and shape of the opening. Wind is trickier, but is generally treated similarly. I know the relevant equations are in the Liddament books, but can't remember specifically where. 

So I wanted to start with a basic who can help then go into more detail later. 
But yes find the air flows through the openings and area of the openings. 

I've approached it now as airflow/m^2 of opening then used air rates per person (EN 13770:2004) to specify a target rate for winter and summer and size the openings from that.

This hasn't been the most precise and consistent course and assignment I've ever carried out.   

My tutor got back to me and while areas don't quite feel right a little to much assumptions and things not quite adding up in the examples I'm slowly moving on. 
We have a certain amount of freedom to manipulate the design so to simplify things I've closed off L1 as suggested by the tutor. 
The thing that got me was having calculated the stack pressure based on the lowest opening and then added the wind how do I determine the flow networks.

The examples have the flow rates calculated end to end so combining the pressures W3 and L2 for the air flow right through the building. Treating each floor as individual zones.
Now the assignment is only meant to represent very early calculation estimates so I guess this is ok, personally I'd then move to use CFD software after the heavily simplified systems for better predictions. 

RSS

Forum Discussions

Electro Magnetic Fields (EMF)

Started by Barry L NewDelman in General Forum. Last reply by Arnie Katz 15 hours ago. 2 Replies

Affordable Housing Funding

Started by SUZETT MOFFITT in General Forum. Last reply by Diane Chojnowski yesterday. 4 Replies

Latest Activity

Dave Ransom joined James Sayers's group
Thumbnail

Marketing Energy Efficiency

Sharing ideas, tools and examples of promoting energy efficiency to consumersSee More
4 hours ago
Dave Ransom joined Diane Chojnowski's group
Thumbnail

Tools of the Trade

A hammer and a saw used to be the key tools for home contractors. Today, the best-in-breed also use…See More
4 hours ago
Dave Ransom joined Michael Stuart's group
Thumbnail

INFRARED THERMOGRAPHY USERS

This group is dedicated to knowledge sharing and discussion of infrared thermography for building…See More
4 hours ago
Dave Ransom joined Sean Lintow Sr's group
Thumbnail

Best Practices (Residential)

Best Building, Retrofitting, or even Auditing Practices - what are they, what should change, what…See More
4 hours ago

Photos

Loading…
  • Add Photos
  • View All

© 2017   Created by Lawrence Berkeley National Laboratory.   Powered by

Badges  |  Report an Issue  |  Terms of Service