(1) Kev ntsuas kub ntawm ib sab phab ntsa raws li qhov kub thiab txias ntawm cov kua dej kub;
(2) Xam cov cua sov hloov coefficient ntawm sab no siv cov qauv kev sib npaug sib npaug;
(3) Xam cov nqi pauv kub q1 rau ib cheeb tsam ntawm sab no siv cov qauv q1=a1 (t1 tw1);
(4) Xam cov phab ntsa kub tw2 ntawm sab nraud siv cov qauv tw2=tw1-q1Rp raws li qhov thermal resistance Rp ntawm lub phaj kub exchanger phaj;
(5) Xam cov cua sov hloov coefficient a2 ntawm sab nraud siv qhov sib npaug sib npaug;
(6) Xam cov nqi pauv kub q2 rau ib cheeb tsam uas siv cov qauv q2=a2 (tw2-t2). Yog tias qhov ntsuas kub ntawm phab ntsa yog qhov tseeb, ces q1=q2 yuav tsum siv; Yog tias q1 ≠ q2, phab ntsa kub yuav tsum tau rov xav dua ua ntej xam kom txog thaum q1 thiab q2 yog qhov sib npaug.
Rau kev xam kom raug thiab ceev, cov khoos phis tawj tuaj yeem siv tau; Xwb, siv cov duab nraaj siv tau, piv txwv li ntau qhov kub ntawm phab ntsa, los ntsuas qhov ntsuas q1 thiab q2, qhov chaw sib tshuam ntawm q1 thiab q2 yog phab ntsa kub.