Stale Air Test to 199C
In this test we compared the energy used to heat up oil with and without a glass tube trapping stale air around the receiver pipe using the vertical pipe test unit. Please find a link to the video at video 27 heating oil to 199C
We used a Pyrex tube around the black metal receiver tube.
We filled the metal pipe with 1.7 Litres of vegetable oil. First the oil was heated with only the metal pipe. The same test was then done with the Pyrex tube and stale air around the metal pipe. The oil was heated all the way to 199C which is the limit of my oven thermometer.
As you can from the graphs below the test with stale air insulation heated up much fast in the same sun conditions.
This shows the the stale air allows virtually all sun energy into the pipe and does provide some insulation again heat loss. More testing is required with a vacuum (see 4x2ft Test Unit stale air vs vacuum test). The graph below shows the stale air insulation test heating oil all the way to 199C.