Article 40570 of sci.engr.heat-vent-ac: Path: news.misty.com!not-for-mail From: nicksanspam@ece.villanova.edu Newsgroups: sci.engr.heat-vent-ac,alt.home.repair Subject: Re: Still interested in purely-radiant cooling. Date: 16 Aug 2008 20:02:42 -0400 Organization: Villanova University Lines: 38 Message-ID: References: <264fefe7-4fe8-470b-bc53-d43b886ed5a3@w39g2000prb.googlegroups.com> NNTP-Posting-Host: acadia.ece.villanova.edu X-Trace: max.inside.misty.com 1218931364 6306 153.104.44.130 (17 Aug 2008 00:02:44 GMT) X-Complaints-To: abuse@misty.com NNTP-Posting-Date: Sun, 17 Aug 2008 00:02:44 +0000 (UTC) Xref: news.misty.com sci.engr.heat-vent-ac:40570 alt.home.repair:1039701 <.p.jm@see_my_sig_for_address.com> wrote: >>... Some buildings have chilled beams and ceilings for cooling. > > So do many many cold rooms of various applications. Ever hear >of static-coil ammonia systems ? No. I'm mainly interested in houses, altho I've read that a 70 F low-e ceiling can reduce ice rink melting by 10 watts/ft^2... >They do not work primarily by raidant absorption, they work mainly by >convection currents. Cool air falls... >If you were to put the coils at the floor instead of the ceiling, they >wouldn't work worth a shit. There would be more cool surface, but maybe less cooling, with no slow ceiling fan. >>... a cool floor would make more sense, since warm air rises. A slow >>ceiling fan with an occupancy sensor and a room temp thermostat could >>stir up some floor air as needed for comfort. > > And thus, it is no longer a radiant system, it is convective. Most of the cooling might be convective, but consider that a) a ceiling needs well-distributed cool sources in order to have a large radiant or convective surface, but we might cool an entire floor with a single point source, since cool air falls, and b) a slow ceiling fan can provide more air velocity for useful low-energy cooling, allowing a higher room air temp for the same comfort, and c) a radiant cool floor can allow a higher air temp, for the same comfort, and d) with a slow ceiling fan, it's easier to turn off the cooling when nobody's in the room. Nick