Net-exergetic, hydraulic and thermal optimization of coaxial heat exchangers using fixed flow conditions instead of fixed flow rates

Geothermal Energy

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Table 6 Thermal Results as total borehole resistance \({R_b^*}\) [mm K/W] for several scenarios

\({c}\)[-]	\({\lambda }\)[W/ mK]				\({L}\)[m]		\({\text{SDR}}\)[-]		\({r_o}\)[m]		\({Re}_{{c}}\)[-]
	Stand.	Switch	Plastic	Steel	100	5	6	41	min	max	\(4\cdot 10^3\)	\(10^5\)
	Laminar
0.010	56.94	104.03	104.03	56.94	92.67	35.06	56.94	56.94	70.38	37.79
0.108	49.55	96.66	96.64	49.56	71.56	31.88	49.54	49.56	58.82	34.19
0.206	44.81	91.94	91.90	44.85	63.43	29.32	44.78	44.83	52.58	31.36
0.304	40.30	87.47	87.40	40.38	56.34	26.77	40.26	40.35	46.88	28.56
0.402	35.74	82.95	82.84	35.85	49.35	24.12	35.70	35.80	41.20	25.66
0.500	31.01	78.25	78.11	31.16	42.23	21.34	30.97	31.09	35.38	22.62
0.598	26.04	73.30	73.14	26.20	34.93	18.35	25.99	26.11	29.36	19.36
0.696	20.72	68.00	67.82	20.90	27.41	15.09	20.68	20.79	23.04	15.81
0.794	14.96	62.24	62.05	15.14	19.66	11.42	14.91	15.01	16.37	11.82
0.892	8.56	55.84	55.66	8.74	11.69	7.05	8.52	8.62	9.25	7.12
0.990	1.25	48.53	48.35	1.43	3.47	1.13	1.22	1.32	1.57	0.92
	Turbulent
0.010	1.99	49.09	49.09	1.99	2.08	1.90	1.99	1.99	2.07	1.70	12.25	0.56
0.108	2.42	49.54	49.52	2.44	2.58	2.32	2.42	2.43	2.51	2.12	13.92	0.62
0.206	2.50	49.62	49.60	2.53	2.65	2.40	2.50	2.51	2.58	2.20	13.84	0.63
0.304	2.48	49.61	49.58	2.51	2.61	2.38	2.48	2.49	2.56	2.18	13.30	0.63
0.402	2.38	49.52	49.48	2.42	2.50	2.30	2.38	2.39	2.46	2.10	12.44	0.62
0.500	2.22	49.36	49.32	2.26	2.32	2.15	2.22	2.23	2.29	1.94	11.29	0.59
0.598	1.99	49.13	49.09	2.03	2.07	1.94	1.99	2.00	2.06	1.73	9.86	0.56
0.696	1.69	48.83	48.79	1.74	1.76	1.66	1.69	1.70	1.76	1.44	8.15	0.52
0.794	1.33	48.47	48.43	1.37	1.39	1.31	1.33	1.33	1.39	1.09	6.12	0.47
0.892	0.90	48.04	47.99	0.94	0.94	0.89	0.89	0.90	0.95	0.66	3.70	0.41
0.990	0.39	47.54	47.49	0.44	0.43	0.39	0.39	0.39	0.44	0.16	0.70	0.34