Test

     var temp1 = board.create('glider', [2,2,heatexchanger1], {strokeColor:'#00f', fillColor:'#00f', size:10, name:'T1'});

     var temp2 = board.create('glider', [10,2,heatexchanger2], {strokeColor:'#f00', fillColor:'#f00', size:10, name:'T2'});

     var deltaT = board.create('segment', [temp1, temp2], {strokeColor:'#000', strokeWidth:2});

     var label = board.create('text', [8, 7, function(){return 'ΔT = ' + Math.abs(temp1.Y() - temp2.Y()).toFixed(1) + ' K';}], {fontSize:18});

//board.update();