There is an engineering cost trade off between the length of the experiment (hence integral of power) and the volume of water. For the definitive long duration bulk calorimetry tests people demand. At a few weeks duration (as apparently Rossie was forced to do by his potential customers) we're dealing in GJs anomalous heat.
Do the arithmetic. The smaller the volume of water, the larger the temperature change over the course of the experiment and this can confound your efforts to get isothermal conditions in the water's contact with the external surfaces. Agreed, if the floor temperature changes much, even if you control the room temperature, it will affect the measurements substantially. You can address that by placing the pool on an insulating bed made of styrofoam. Controlling the room's air temperature really isn't that big of a deal. Humidity is handled by the supplied pool cover -- very little air exchange occurs if you cover the 4 or 5 1" holes and tighten the cord. A rough estimate of the energy required for 1C change in such a pool <http://www.walmart.com/ip/39264346>: (15ft/2)^2*pi*48in;calorie/ml/deltaK;deltaK?joules <http://www.testardi.com/rich/calchemy2/> ([{([{15 * foot} / 2]^2) * pi} * {48 * inch}] * [{calorie / (milli*liter)} / deltaK]) * deltaK ? joule = 8.3802985E7 joules On Mon, Jun 15, 2015 at 3:52 PM, Jed Rothwell <[email protected]> wrote: > James Bowery <[email protected]> wrote: > >> >> Go to Walmart. Buy an above-ground swimming pool for a few hundred >> bucks. Install it in a basement or anywhere the temperature can be >> controlled to within a degree or so. Fill it. Turn on the filter pump to >> circulate water. Put the apparatus in it. >> > > Based on my experiences with hot tubs and the like, I think this would be > an inaccurate method. In testing, I think you would find that losses vary a > great deal from things like room temperature, floor temperature, humidity, > the placement of the cover over the pool and so on. I recommend a much > smaller body of water in a better insulated container. > > - Jed > >
