Welcome to the Solar Collector
Brainstorming and Development Page!


 

Home

Hot Air Collector

Hot Water Project 1

Hot Water & Space Heating

Solar Electric

Solar Construction 101

FAQs

Best Collectors

Simply Solar
Register Calendar Latest Topics
 
 
 


Reply
  Author   Comment   Page 19 of 19     «   Prev   16   17   18   19
gbwillson

Avatar / Picture

Registered:
Posts: 2,247
Reply with quote  #181 
JC-

Here are a couple of example of small tests and discussions about reflective versus black interiors.

http://simplysolar.supporttopics.com/post/black-absorbent-interior-vs-reflecitve-radiant-interior-6756917?highlight=reflective&trail=10

Here's another discussion...
http://simplysolar.supporttopics.com/post/black-box-vs-reflective-box-when-using-black-screen-8211084?highlight=silver+back&trail=10

For my ZP collectors I always use two screen layers closest to the back of the collector and a single layer of screen closest to the glazing. I wanted more of the heat from the sun to stay in the screen gap where it can be heated by the screens instead of the back surface of the collector. With three layers, I really can't see the back of the collector, and if I could, the light would have to bounce back through three layers to escape the collector box. 

If you want to test on your own, you would need to build two identical test units with the only difference being the reflective surface. Simply testing a white surface and then painting it black and testing again wouldn't be a fair test since the conditions wouldn't be the same. 

Greg in MN


gbwillson

Avatar / Picture

Registered:
Posts: 2,247
Reply with quote  #182 
Quote:
Originally Posted by JC77
The way I'm understanding a zero pass, the air between the top screen and the glazing is mildly stagnated along with the air between the rear screen and the back of the collector. The two layers of screen basically act as hot walls the air passes between/around? It obviously has to interact with the screen to pick up heat. Anyway, I read a lot of discussion on low mass collectors being better at getting heat out of the absorber material and wondered of doubling up the screen on each layer and painting everything else white would have a reflective effect to put more energy in the absorbing material (screens) and less into the collector.


JC-

On a ZP collector, the air outside the screen gap is not actually stagnated as there is minimal movement of air in and out of the gap via the openings in the screen. At higher air velocities, which the ZP needs, most of the fast moving air stays between the screen gap. This also helps keep the bulk of the airflow somewhat isolated from the cold glazing. You DO want the air to "mingle" with the surface of the screens to break up the laminar flow. So a rough surface mesh or screen with many surfaces works very well at transferring heat to the air. I use a double layer of screen for the back of the collector, and only single layer on the front which still allows much of the sunlight to hit the back screen layers and keep the heated screen on top and bottom of the moving air.

Greg in MN
JC77

Registered:
Posts: 15
Reply with quote  #183 
Thanks Greg. I think that settles the argument for white or reflective. I'm kind of surprised it's only a ten percent difference. I understand I'd need two identical collectors to do a side by side test. I've since switched my plans on my hydronic system to closed loop so now the locations that were going to get solar air heaters could have solar water heating panels instead. I can use hot water year round so I'm giving up on solar air heating panels for now.
Previous Topic | Next Topic
Print
Reply

Quick Navigation:

Easily create a Forum Website with Website Toolbox.

 

web statistics