I need to know how much the water temperature will change in a PVC pipe. I have a 1.2m long PVC pipe filled to 1 meter of water. The inside diameter is 12 inches and the outside diameter is 13 inches. I have a plastic end cap on the bottom and the pipe stands up vertically. I keep it in a 20 degree C room and take it outside for 30 minutes then bring it back in. I lay a thin piece of plastic on top to keep the sun off the water. I want the temperature to stay at 20 degrees. Let's say the temperature outside is 100 F. How do I calculate how fast the temperature will change? Thanks.