namespace path   {::tcl::mathop ::tcl::mathfunc} 
set Nu_combined [ - [ + 0.40 0.32 ]  [* 0.40 0.32 ]  ]
answer% 0.592 for measured efficiencies
set carnotefficiency_gas_turbine [ carnotthermic 1700 900]
answer% 0.4705 or 47 percent
set novikovefficiency_gas_turbine [ endothermic 1700  900]
answer% 0.272
set carnotefficiency_steam [ carnotthermic  900 400]
answer% 0.555
set novikovefficiency_steam [ endothermic  900 400]
answer% 0.33
set Nu_combined_Novikov [ - [ + 0.272 0.33 ]  [* 0.272 0.33 ]  ]
answer% 0.512 for Novikov estimated efficiencies

One MMBtu = 1,000,000 Btu
mass_flow_rate = burning_area* fuel_burn_rate*fuel_density
   where fuel_burn_rate= initial_rate +  (e**+c*kelvin)

testcase number: 6
max room fuel kg 2705.181
                                     

        # pretty print from autoindent and ased editor
        # heat engine combustion calculator
        # written on Windows XP on eTCL
        # working under TCL version 8.5.6 and eTCL 1.0.1
        # gold on TCL WIKI , 9aug2013
        package require Tk
        namespace path {::tcl::mathop ::tcl::mathfunc}
        frame .frame -relief flat -bg aquamarine4
        pack .frame -side top -fill y -anchor center
        set names {{} {combustion chamber diameter meters:} }
        lappend names {combustion chamber height meters:}
        lappend names {heat source temperature input: }
        lappend names {heat sink temperature input: }
        lappend names {answer: volume cubic meters}
        lappend names {total heat units, megajoules:}
        lappend names {endo process, applied/total energy: }
        foreach i {1 2 3 4 5 6 7} {
    label .frame.label$i -text [lindex $names $i] -anchor e
    entry .frame.entry$i -width 35 -textvariable side$i
grid .frame.label$i .frame.entry$i -sticky ew -pady 2 -padx 1 }
        proc about {} {
            set msg "Calculator for Heat Engine Combustion
            from TCL WIKI,
            written on eTCL "
            tk_messageBox -title "About" -message $msg }
        proc pi {} {expr acos(-1)}
        proc pistonvolumex { d h } {
            set  pistonvolumexxx [* .25 [pi] $d $d $h ]
            return $pistonvolumexxx
            }
        proc heatx { vol density } {
            set fuel_mass [* $vol $density]
            set total_heat [* $fuel_mass 40.1]
            return $total_heat
            }
        proc endothermic { theatsource tlow  } {
            set endo [expr { 1.-sqrt($tlow)/sqrt($theatsource)} ]
            return $endo
            }
        proc carnotthermic { theatsource tlow  } {
            set theatsource [* 1. $theatsource]
            set tlow  [* 1. $tlow]
            set carnot [- 1. [/ $tlow $theatsource]]
            return $carnot
            }
        proc endoprocess { theatsource tlow  } {
            set theatsource [* 1. $theatsource]
            set tlow  [* 1. $tlow]
            set endoprocess [* .25 [- 1. [/ $tlow $theatsource]]]
            return $endoprocess
            }        
        proc firebox { total_heat burn_time cross_section temp_ambient temp_flame} {
            set d $cross_section
            set firing_temp 1
            set heat_flux [/ $total_heat $burn_time]
            set heat_flux_persec [/ $heat_flux $burn_time]
            set cross_section [ / [* [pi] $d $d ] 4.]
            set item 25
            set temp_ambient 25
            set temp_flame 1488.
            set tx  $temp_ambient
            set taxx $temp_flame
            set t 25
            set h [/ $heat_flux_persec $cross_section]
            while {$item <= 4000} {
                incr item
                set t [+ $t 1 ]
                set term1 [* 1. $t $t $t $t]
                set term2 [* 1. $tx $tx $tx $tx]
                set term1 [* .000000000056703 [ - $term1 $term2]]
                set term2 [* $h  1.1 [/ [- $taxx $t]  [ - $taxx $tx ]]]
                set difference  [abs [- $term1 $term2]]
                if {$difference < 2.} { set temp_answer $t }
                }
            return $temp_answer
                }
        proc calculate {     } {
            global answer2
            global side1 side2 side3 side4 side5
            global side6 side7 testcase_number fuel
            global piston_volume piston_temperature_exp
            global workdays total_heat massfromvolume
            global total_heat firebox_temp heatsourcetemp2
            global carnotefficiency novikovefficiency
            global idealappliedovertotal piston_firing_time
            global heatsinktemp1
            incr testcase_number
            set piston_diameter $side1
            set piston_height $side2
            set piston_firing_time [* 2 60 10]
            set heatsourcetemp2 $side3
            set heatsinktemp1 $side4
            set piston_volume 1
            set piston_volume [pistonvolumex $piston_diameter $piston_height]
            set fuel_density 850
            set massfromvolume [* $piston_volume $fuel_density]
            set fuel [* [ /  8.2 60.   ] $massfromvolume]
            set total_heat [* 13.5 $fuel]
            set temp_amb 25.
            set temp_flame 1488.
            set piston_temperature_exp $temp_flame
            set total_heat_joules [* $total_heat 1.0E6]
            set firebox_temp [firebox $total_heat_joules $piston_firing_time $piston_diameter $temp_amb $temp_flame]
            if  {$piston_temperature_exp > 1200.} {set piston_temperature_exp 1200}
            set workdays [/ $piston_volume 3. ]
            set carnotefficiency [ carnotthermic $heatsourcetemp2 $heatsinktemp1]
            set novikovefficiency [ endothermic $heatsourcetemp2 $heatsinktemp1]
            set idealappliedovertotal [ endoprocess $heatsourcetemp2 $heatsinktemp1]
            set fractionwork [ endoprocess $heatsourcetemp2 $heatsinktemp1]
            set side5 $piston_volume
            set side6 $total_heat
            set side7 $fractionwork  }
        proc fillup {aa bb cc dd ee ff gg} {
            .frame.entry1 insert 0 "$aa"
            .frame.entry2 insert 0 "$bb"
            .frame.entry3 insert 0 "$cc"
            .frame.entry4 insert 0 "$dd"
            .frame.entry5 insert 0 "$ee"
            .frame.entry6 insert 0 "$ff"
            .frame.entry7 insert 0 "$gg"}
        proc clearx {} {
            foreach i {1 2 3 4 5 6 7} {
                .frame.entry$i delete 0 end } }
        proc reportx {} {
            global side1 side2 side3 side4 side5
            global side6 side7 testcase_number fuel
            global piston_temperature massfromvolume
            global piston_volume workdays
            global total_heat firebox_temp
            global piston_temperature_exp
            global carnotefficiency novikovefficiency
            global idealappliedovertotal
            global piston_firing_time heatsourcetemp2
            global heatsinktemp1
            console show;
            puts "testcase number: $testcase_number"
            puts "piston diameter meters: $side1 "
            puts "piston height meters: $side2 "
            puts "piston firing seconds: $piston_firing_time "
            puts "volume cubic meters: $side5 "
            puts "total energy MJ: $side6 "
            puts "piston volume m*m*m: $piston_volume "
            puts "heat source temperature T2 $heatsourcetemp2"
            puts "heat sink temperature T1 $heatsinktemp1"
            puts "max room fuel kg $massfromvolume"
            puts "estimated fuel, kg $fuel"
            puts "total heat megajoules $total_heat"
            puts "firing max temperature  $firebox_temp "
            puts "man workdays to load fuel  $workdays"
            puts "Carnot  efficiency $carnotefficiency"
            puts "Novikov efficiency $novikovefficiency"
            puts "ideal applied/total $idealappliedovertotal "
            }
         frame .buttons -bg aquamarine4
        ::ttk::button .calculator -text "Solve" -command { calculate   }
        ::ttk::button .test2 -text "Testcase1" -command {clearx;fillup .5 .5 900. 300. 0.0981  153.9 .166 }
        ::ttk::button .test3 -text "Testcase2" -command {clearx;fillup 1.5 1.5 1200. 300. 2.65  4156. .1875 }
        ::ttk::button .test4 -text "Testcase3" -command {clearx;fillup 2. 2. 1400. 300. 6.28  9853. .196 }
        ::ttk::button .clearallx -text clear -command {clearx }
        ::ttk::button .about -text about -command about
        ::ttk::button .cons -text report -command { reportx }
        ::ttk::button .exit -text exit -command {exit}
        pack .calculator  -in .buttons -side top -padx 10 -pady 5
        pack  .clearallx .cons .about .exit .test4 .test3 .test2   -side bottom -in .buttons
        grid .frame .buttons -sticky ns -pady {0 10}
        . configure -background aquamarine4 -highlightcolor brown -relief raised -border 30
        wm title . "Heat Engine Combustion Calculator "       

  puts " %| testcase $testcase_number | value| units |comment |%"
  puts " &| volume| $volume| cubic meters |based on length $side1 and width $side2   |&"  

        # pretty print from autoindent and ased editor
        # Novikov efficiency of small gas stoves
        # written on Windows XP on eTCL
        # working under TCL version 8.5.6 and eTCL 1.0.1
        # gold on TCL WIKI , 8aug2013
        package require Tk
        namespace path {::tcl::mathop ::tcl::mathfunc}
        console show
       proc novikov { theatsource tlow  } {
            set endo [expr { 1.-sqrt($tlow)/sqrt                        ($theatsource)} ]
            return $endo
            }
        proc carnot { theatsource tlow  } {
            set theatsource [* 1. $theatsource]
            set tlow  [* 1. $tlow]
            set carnot [- 1. [/ $tlow $theatsource]]
            return $carnot
            }
        proc k { temperature  } { 
             set temperature [+ $temperature 273. ]  
             return $temperature
             }
  puts "%|name|water boiled|measured Nu|Novikov Nu|Carnot Nu |%"
  puts "&|stove a|1 l|49.4|[* 100 [novikov 96.5 32.]]|[* 100. [carnot 96.5 32.]]|&"
  puts "&|stove b|1 l|43.8|[* 100. [novikov 95.5 24.5]] |[* 100. [carnot 95.5 24.5]] |&"
  puts "&|stove c|0.5 l|32.4|[* 100. [novikov 96.5 24.]] |[carnot 96.5 24.]|&"