A natural gas thermal unit equals what equivalent amount of liquid propane gas?

Answer 1

First, what is a "natural gas thermal unit"? Are you talking about a therm? And what is liquid propane gas? How can it be a liquid and a gas? Are you talking about liquid propane, which is the fuel in your barbeque grill? That stuff is in liquid form because it's pressurized. When it comes out of the tank, it turns back into a gas, so one would imagine that your so-called "natural gas thermal unit" would apply. But let's assume you meant "therm." A therm is a unit of energy that is equal to 100 thousand BTUs (British Thermal Units). That is about the amount of heat energy liberated by 100 cubic feet (Ccf) of natural gas. But propane has an equivalent energy capacity of about 2500 BTUs per cubic foot, so that translates to 250,000 BTUs per Ccf -- two and half times greater than the rule of thumb I just stated!! -- which is 2.5 therms per Ccf. So, I guess the question would becomes "What amount of gaseous propane -- at standard temperature and pressure -- is equivalent to one gallon of liquid propane?" The way I figure it, one gallon of liquid propane will produce about 36.6 cubic feet of gas.1 So, a 20-pound tank (which holds 4.1 gallons of liquid propane gas) is equal to about 150 cubic feet (or 1.5 Ccf) of gaseous propane. ______________ 1. And the way I figured it is this: Propane can liberate about 2500 BTUs per cubic foot. We also know it can liberate 91,600 BTUs per liquid gallon. So I divided 91.6E3 by 2.5E3 to get 36.6 cu.ft./gal.