It was observed from the numerical computations

Upper glass cover:equation(376)ht,fw−g2(Tfw−Tg2)bdx=ht,g2−a(Tg2−Ta)bdxht,fw−g2(Tfw−Tg2)bdx=ht,g2−a(Tg2−Ta)bdx
Flowing water:equation(377)ht,g1−fw(Tg1−Tfw)bdx=m?fwCfwdTfwdtdx+ht,fw−g2(Tfw−Tg2)bdx
Lower glass BX 471 cover:equation(378)ht,w−g1(Tw−Tg1)=ht,g1−fw(Tg1−Tfw)ht,w−g1(Tw−Tg1)=ht,g1−fw(Tg1−Tfw)
Lower water mass:equation(379)hc,b−w(Tb−Tw)+Qu=MwCwdTwdt+ht,w−g1(Tw−Tg1)
Basin liner:equation(380)α′bI(t)s=hc,b−w(Tb−Tw)+hb(Tb−Ta)α′bI(t)s=hc,b−w(Tb−Tw)+hb(Tb−Ta)whereequation(381)Qu=AaFR[(ατ)effI(t)C−ArULCAa(Tw−Ta)]
It was observed from the numerical computations that the temperature of water in the lower basin is increased in comparison with single effect distillation due to the reduced upward heat losses. But the hourly output in the lower basin is reduced due to the reduced temperature difference between the water and glass temperatures. However the overall output is increased due to reutilization of the latent heat of evaporation in the second effect.