[Carno]

I am trying hard to simulate a heat exchanger problem, in which hot gas is getting cooled by water.
I am getting strange error.
The density of water starts to reduce and run crashes after some time. One more thing is, gas is at higher temperature, but instead of getting cooled by water it's temperature goes on increasing. I am also posting my water thermo file file.

Time = 1


Solving for fluid region gas
DILUPBiCG:  Solving for Ux, Initial residual = 1, Final residual = 0.005866799, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 1, Final residual = 0.001537743, No Iterations 1
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 0.0001546412, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 1, Final residual = 0.00229472, No Iterations 1
Min/max T:300 500.0004
GAMG:  Solving for p_rgh, Initial residual = 0.9955299, Final residual = 0.008126581, No Iterations 6
GAMG:  Solving for p_rgh, Initial residual = 0.2520469, Final residual = 0.002157155, No Iterations 4
time step continuity errors : sum local = 0.09586636, global = -0.009241943, cumulative = -0.009241943
Min/max rho:0.6966167 1.161028

Solving for fluid region water
DILUPBiCG:  Solving for Ux, Initial residual = 1, Final residual = 0.0001699618, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 1, Final residual = 0.0002200249, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 1, Final residual = 0.0003723527, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 0.9999999, Final residual = 0.003414167, No Iterations 1
Min/max T:300 300
GAMG:  Solving for p_rgh, Initial residual = 0.5623218, Final residual = 0.003571359, No Iterations 3
GAMG:  Solving for p_rgh, Initial residual = 0.147112, Final residual = 0.001033737, No Iterations 3
time step continuity errors : sum local = 2.067321, global = 0.05357055, cumulative = 0.0443286
Min/max rho:800.4 800.4

Solving for solid region solid
DICPCG:  Solving for h, Initial residual = 1, Final residual = 0.002423683, No Iterations 1
DICPCG:  Solving for h, Initial residual = 0.1074138, Final residual = 0.0002562218, No Iterations 1
Min/max T:300 300.8638
ExecutionTime = 2.973 s  ClockTime = 3 s

Time = 98


Solving for fluid region gas
DILUPBiCG:  Solving for Ux, Initial residual = 0.02985441, Final residual = 0.0002924578, No Iterations 1
DILUPBiCG:  Solving for Uy, Initial residual = 0.02355236, Final residual = 3.896382e-006, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 0.03269479, Final residual = 1.82892e-005, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 0.02673384, Final residual = 4.620732e-005, No Iterations 1
Min/max T:-39.81789 1329.228
GAMG:  Solving for p_rgh, Initial residual = 0.2301746, Final residual = 0.002083338, No Iterations 3
GAMG:  Solving for p_rgh, Initial residual = 0.0461193, Final residual = 0.0003474025, No Iterations 4
time step continuity errors : sum local = 0.4076185, global = -0.04073103, cumulative = 0.08418367
Min/max rho:0.3814168 3.729872

Solving for fluid region water
DILUPBiCG:  Solving for Ux, Initial residual = 0.009072544, Final residual = 3.09553e-006, No Iterations 2
DILUPBiCG:  Solving for Uy, Initial residual = 0.008195855, Final residual = 2.820889e-006, No Iterations 2
DILUPBiCG:  Solving for Uz, Initial residual = 0.01254545, Final residual = 2.22747e-006, No Iterations 2
DILUPBiCG:  Solving for h, Initial residual = 0.04108215, Final residual = 0.0002185422, No Iterations 1
Min/max T:300 300.0001
GAMG:  Solving for p_rgh, Initial residual = 0.01375531, Final residual = 7.775061e-005, No Iterations 3
GAMG:  Solving for p_rgh, Initial residual = 0.003404876, Final residual = 2.465606e-005, No Iterations 3
time step continuity errors : sum local = 0.0003594424, global = 2.956881e-005, cumulative = 0.08421323
Min/max rho:10 10

Solving for solid region solid
DICPCG:  Solving for h, Initial residual = 0.000905289, Final residual = 1.451611e-006, No Iterations 1
DICPCG:  Solving for h, Initial residual = 0.0009011053, Final residual = 1.444383e-006, No Iterations 1
Min/max T:300 302.7423
ExecutionTime = 117.898 s  ClockTime = 117 s

FoamFile
{
	version	2.0;
	class	dictionary;
	format	ascii;
	location	"constant/water";
	object	thermophysicalProperties;
}
thermoType
{
	type	heRhoThermo;
	mixture	pureMixture;
	transport	const;
	thermo	hConst;
	equationOfState	rhoConst;
	specie	specie;
	energy	sensibleEnthalpy;
}
mixture
{
	specie
	{
		nMoles	1.0;
		molWeight	18.0;
	}
	thermodynamics
	{
		Cp	4180.0;
		Hf	0.0;
	}
	transport
	{
		mu	0.001;
		Pr	7.01;
	}
	equationOfState
	{
		rho	998.0;
	}
}