|
Message
Boy, you catch me every time{:>)
Thanks for the info Rusty
Paul,
I calculate out Rusty's radiator
to have a volume of 17.5*24.25*2.25 = 964 in^3. Given that he was running
a turbo, he would naturally want/need more cooling capacity than a NA
block. So his basic radiator was approx 50% large in volume than two
cores. Since he could produce up to that much additional power with his
turbo, it would appear that his is sized about right - perhaps a bit on the
large size since he probably would not run under high boost at
cruise.
I won't go into the different configurations
he tried, but it appears he intends to go with 300 square inch area which with a
core depth of 2.25 inches would give him around 675 in^3 - again fairly close to
the area of two evaporator cores.
So again, I would not recommend you spending
a lot of money on a possibly undersized radiator.
You can fairly accurately calculate your cooling
needs - and your radiator builder should be able to tell you what size you
need. You probably need to let him know what air flow speed you are
expecting it to provide that performance under. If your radiator builder
knows what he is doing he should be able to take the BTUs you need to reject and
the air flow and calculate the size of radiator you need. On the other
hand, if he is just going to whip you up an "automobile" style radiator, then
you could be stuck with just auto level cooling - perhaps insufficient for high
power continuos operation.
My calculations shows that at 175Hp you need to get
rid of around 5400 BTU/Min though the radiator and another 2700 BTU/Min through
the oil cooler. At 160Hp that would be around 5000 and 2500 btu
respectively. Since that is probably worst case (take off and initial
climbout), you might want to size the radiator for your cruise power setting and
plan on a bit of over temp on take off an climb out. At a high power
cruise setting (75%) you would need to cool 131 HP and that would drop your
cooling requirements to around 4000 and 2000 btu/min respectively.
Any descent radiator design shop should be able to work with that type of
information to get you close in size. If you are constrained by the 17x8
area then perhaps a thicker radiator might be the answer. My
calculations indicates that with a 17X8 you would need a radiator approx 5"
thick to equal the core volume of two evaporator cores.
However, a 5" thick radiator would require more
dynamic airpressure (high airspeeds) than our 3.6" thick cores. While I
think you would do Ok with that thickness once airborne and at higher airspeeds,
you might have ground cooling problems unless somehow aiding the airflow though
the radiator. But, at least I am confident you could cool adequately at
cruise.
But, in any case, I think your currently planned
radiator size is undersized. FWIW - always keepin mind my knowledge
of radiators and cooling is quite limited.
Ed
----- Original Message -----
Sent: Wednesday, November 19, 2003 3:06
PM
Subject: [FlyRotary] Re: Core vs Radistor
was Re: [FlyRotary] radiator
Rusty, what was the size of your radiator
and the final determination about its adequacy?
Ed
This is
revenge for those engine out comments, isn't it :-)
I started
with a huge radiator, because it had (alleged) oil coolers in it.
The oil coolers didn't work out, and were bypassed, leaving only water
cooling.
The rad core width is 17.25, and the length as been
changed. Full length is
24.25” (423 sq in) . The length (not covered) was first tested at 17.75 " (306 sq in) . The final length (not covered) was
12.625” (218 sq in) . HALF the original radiator. The core is 2.25” thick if anyone is
doing the math . The
other thing to consider is that the covered portion of the radiator is only
covered on the front side. The back side is open. While there is
no air passing through, turbulent air around the back side will still be
removing some heat from the covered section. There is also a 2"
thick oil cooler behind the uncovered area of radiator, so overall, this
is about 4.5" thick.
Here is a chart of inlet, rad size, and temps for climb at
around 100- 110 mph. The cheek outlet is fixed at about 66
sq in, and the bottom opening is
about 83 sq in. OAT is
ground temp, not in-flight.
Date
|Inlet (sq in)| Rad core
(sq in) | water temp F | oil temp F | OAT |
comments
80 |
423 | <180 (t-stat) | 180 | 80 | bottom outlet open
80 |
306 | <180 (t-stat) | 180 | 80 | bottom outlet open
10-18 | 48 |
306 |
180 (no t-stat) | 230 | 75
10-18 | 80 |
218 |
160 (no-t-stat) | 185 (not max?) | 70
10-19 | 80 | 218
| 160 (no-t-stat) | 220+
| 80
11-01 | 80
| 218
| 160 (no t-stat) | 200
| 80 | bottom outlet open
My current (changes every week)
plan is to go with a core that is still 2.25" thick, but gives me about 300 sq
inches of frontal area. That will be more than I need now, but
since I'll be putting the oil cooler in front of it to lower the oil
temps, I'll need more radiator than I do
now.
One final comment about expensive
radiators, I wouldn't buy one, unless you have a very good reason to believe
it will be just what you need. For example, I'll be retiring an $800+
dollar radiator with my rev-2 cowl.
Cheers,
Rusty
|