Lpg Calorific Value - Mongolian Burners

[QldKev]

Been looking at burners lately and have read a few threads on Mongolian burners. I noticed in the pics some are running really clean blue flames, some have more yelow flames; one person said their ring burner was hotter (nothing to do with chilli). Being Mongolian are a low pressure most people are using normal BBQ regs.

LPG has a calorific value around 46.1MJ/kg. Many BBQ regs have a pressure of 2.75kpa (some have 2.8kpa) which is great for Low pressure burners; but the one I was going to use for my burner only has a max flow of 1.5KG/hr. My spare BBQ reg has a max flow of 2.0KG/hr.

Now the
20 Jet Mongolian is rated to 82MJ/hr - 82 / 46.1 = 1.78 KG/hr
23 Jet = 94MJ/hr - 94 / 46.1 = 2.04 KG/hr
32 Jet = 131MJ/hr - 131 / 46.1 = 2.84 KG/hr

So depending on what reg & burner you have you may not be getting the best performance from your burner. A low pressure 2.75kpa reg is available in a 3KG/hr.

Hope this helps.

QldKev

 

[davewaldo]

I'm probably wrong, but pressure and flow rate are two very different things. I thought a burner needs a certain pressure, at which it will burn at a certain rate. So a medium pressure reg might still only feed 2 kg per hour but at a higher pressure. The way I understand it is that the regulator provides a regulated pressure OR a maximum flow rate.

Otherwise a LP reg would do almost any burner as even the rambos use less than 2kg for a 1 hour boil.

 

[QldKev]

Pressure and flow rates are interrelated.

The 2.75kpa reg will produce a max of 2.75kpa at the outlet. If say you had a 2.75kpa-2KG/hr reg with nothing connected to the outlet and turned on the LPG bottle, the most you would loose from your bottle would be 2KG per hour. If you had a 2.75kpa-3KG/hr reg with no backpressure you would loose the 3kg of LPG over the hour. The 3kg/hr reg would have a larger hole to supply the extra flow at the same pressure. In these examples we had zero backpressure on the outlet.

In the real world the hose and burner would introduce back pressure into the system. So to measure how much LPG could be consumed you would need to know what value of the outlet sizes on the burner.

A Rambo burner would have smaller outlets than a Mongolian, hence the Rambo uses a higher pressure reg to flow the same amount of LPG as a Mongolian. The burners should have a MJ/hr rating for a given pressure. The Rambo are rated at 50MJ/hr, but it is not noted at what pressure. Also once we get to the boil we turn down the reg (introduce extra back pressure) to limit the heat output; thus limiting the LPG usage.


QldKev