Radiant Tube Heater Air Preheating for Compact Thermal Efficiency
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Solution Overview
Problem
Gas fired radiant tube heaters face a trade-off between high radiant heat efficiency and overall thermal efficiency, with high radiant efficiency often coming at the expense of reduced overall thermal efficiency, and they tend to be less compact in design.
Innovation Solution
A radiant tube heater design featuring a burner assembly with a pre-mixer chamber, a combustion air pre-heater using residual sensible heat from combustion products, and a secondary air channel, along with a cross-flow type heat exchanger block configuration, which promotes efficient mixing of air and fuel, preheats combustion air, and directs radiant heat efficiently downward.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the heater is designed for high radiant efficiency, then radiant heat efficiency is improved, but overall thermal efficiency deteriorates
Solution Approach 1:
Combustion air is preheated before entering the burner assembly using residual sensible heat from combustion products through a heat exchanger. This preliminary heating action increases the temperature of combustion air, improving overall thermal efficiency while maintaining high radiant heat efficiency by ensuring more complete combustion.
Solution Approach 2:
The residual sensible heat in combustion products, which would normally be wasted, is converted into a useful resource by using it to preheat combustion air through a heat exchanger. This transforms energy loss into energy gain, simultaneously improving both radiant and overall thermal efficiency.
2Loss of energy
If the heater is designed for high radiant efficiency, then radiant heat efficiency is improved, but device compactness deteriorates
Solution Approach 1:
The heat exchanger is integrated within the burner assembly structure, with combustion air channels nested within the burner housing. This nesting arrangement allows the heat exchanger to occupy space within the existing burner assembly volume, achieving high radiant efficiency without increasing the overall heater size.
Solution Approach 2:
The heat exchanger utilizes the vertical dimension by arranging combustion air to flow upward through the burner assembly, utilizing residual heat from combustion products in a compact vertical configuration. This dimensional arrangement maintains compactness while enabling efficient heat transfer.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a higher radiant efficiency while maintaining good overall thermal efficiency and compactness by effectively utilizing residual heat for air preheating and optimizing the heat exchanger configuration, enhancing both radiant energy direction and overall energy utilization.
Implementation Method 1
a plenum chamber and a pre-mixer chamber; the plenum chamber having a combustion air inlet; wherein in use: combustion air flows from said plenum chamber through an orifice to said pre-mixer where said air is mixed with burner fuel
Implementation Method 2
where said air is mixed with burner fuel entering said pre-mixer through said nozzle
Implementation Method 3
where in use at least part of the combustion air supplied to said plenum is preheated in said air pre-heater using residual sensible heat of the hot combustion gas products of the heater
Implementation Method 4
using residual sensible heat of the hot combustion gas products
Implementation Method 5
prior to being combusted at a burner head
Implementation Method 6
Gas fired radiant tube heaters are widely used especially to heat industrial and commercial premises... a high proportion of the potential energy of the fuel gas is converted to radiant heat
Data Source
AI summary
A radiant tube heater with a burner assembly, a radiant tube assembly and a combustion air pre-heater, wherein the burner assembly comprises: a burner fuel nozzle; a plenum chamber and a pre-mixer chamber; the plenum chamber having a combustion air inlet; wherein in use: combustion air flows from said plenum chamber through an orifice to said pre-mixer where said air, is mixed with burner fuel entering said pre-mixer through said nozzle prior to being combusted at a burner head; said pre-mixer being at least partly located within said radiant tube assembly; and where in use at least part of the combustion air supplied to said plenum is preheated in said air pre-heater using residual sensible heat of the hot combustion gas products of the heater.