Research on characteristics of compression-absorption refrigeration system driven by waste heat in liquid-cooled data center

doi:10.11949/0438-1157.20241378

Abstract

Abstract:

Waste heat recovery is an essential solution to optimize the energy consumption structure of data center as well as save energy and reduce carbon emissions. This paper constructed a model of compression-absorption refrigeration system driven by waste heat in liquid-cooled data center, and investigated the influence of supply-side heat source temperatures, cooling water temperature and other parameters on the refrigeration performance. The coordination method of compression ratio and cooling water temperature was researched to compensate for system performance under variable cooling conditions. Combined with the year-round climate analysis in Beijing, the analysis of the refrigeration characteristics driven by waste heat source of a typical server with different heat dissipation powers was carried out, and it was concluded the performance was improved by the increasing temperature of the supply-side heat sources. The operating range of cooling water temperature was widened by 6.5℃ to 8.7℃ as the compression ratio increased from 1.2 to 1.8. In transition seasons and winter, plentiful natural cooling sources can maintain the operation of single-effect absorption refrigeration system with considerable performance, and provide effective natural cooling for servers. During the period of the environmental temperature on average, only a handful of compression power was spent in achieving efficient refrigeration. When operating in the extremely hot climate, the compression power equivalent to 15% to 20% of the waste heat was consumed to maintain efficient refrigeration. The system achieves waste heat recovery with high efficiency in most of the time of the year from the theoretical analysis. In future research, the development of new types of working pairs, the optimization of energy consumption under extreme climatic conditions, and the design and maintenance of system devices are technical difficulties that need to be broken through.

Key words: data center, liquid-cooled system, waste heat recovery, absorption refrigeration, performance compensation

摘要：

余热回收是优化数据中心能耗结构与节能降碳的重要解决方案。构建了液冷数据中心余热驱动的压缩-吸收式制冷系统模型，探究了供给侧热源温度、冷却水温度等参数对系统制冷性能的影响，研究不同冷却条件下提供性能补偿的压缩比-冷却水温度协调方式，结合北京地区的全年气候特征分析了典型服务器在不同散热功率的余热驱动制冷性能。研究得出供给侧热源温度升高使得性能提升，压缩比从1.2增至1.8时冷却水温度范围拓宽6.5~8.7℃；在过渡季或冬季，良好的自然冷源条件可以实现高效的自然冷却或单效吸收式制冷；气温处于平均值的阶段，仅消耗少量压缩电功即可实现高效制冷，而在极端炎热气候下，需要消耗相当于余热量15%~20%的压缩电功以维持高效制冷。

关键词: 数据中心, 液冷系统, 余热回收, 吸收式制冷, 性能补偿

CLC Number:

TK 11⁺5

Congqi HUANG, Shuangquan SHAO. Research on characteristics of compression-absorption refrigeration system driven by waste heat in liquid-cooled data center[J]. CIESC Journal, 2025, 76(S1): 326-335.

黄琮琪, 邵双全. 液冷数据中心余热驱动的压缩-吸收式制冷系统特性研究[J]. 化工学报, 2025, 76(S1): 326-335.

Figures/Tables 14

Fig.1 Compression-absorption refrigeration system

Fig.2 Relationship of P-t-x in compression-absorption refrigeration system

Table 1 Energy conservation of system components

部件	能量守恒关系式
蒸发器	$Q ˙ e v a = m ˙ 1 h 1 - m ˙ 13 h 13 = m ˙ F 1 (h F 1 - h F 2)$
吸收器	$Q ˙ a b s = m ˙ 3 h 3 + m ˙ 9 h 9 - m ˙ 4 h 4 = m ˙ a b s, C 1 (h a b s, C 2 - h a b s, C 1)$
溶液换热器	$m ˙ 5 h 5 + m ˙ 7 h 7 - m ˙ 6 h 6 - m ˙ 8 h 8 = 0$ ; $η e x c = (t 7 - t 8) / (t 7 - t 5)$
发生器	$Q ˙ g e n = m ˙ 10 h 10 + m ˙ 7 h 7 - m ˙ 6 h 6 = m ˙ H 1 (h H 1 - h H 2)$
压缩机	$W ˙ c = m ˙ 3 h 3 - m ˙ 2 h 2 = m ˙ 2 (h 3, i - h 2) / η i$ ; $W ˙ e = W ˙ c / η e$
冷凝器	$Q ˙ c o n = m ˙ 10 h 10 - m ˙ 11 h 11 = m ˙ c o n, C 1 (h c o n, C 2 - h c o n, C 1)$
回热器	$m ˙ 11 h 11 + m ˙ 1 h 1 - m ˙ 12 h 12 - m ˙ 2 h 2 = 0$
溶液泵	$W ˙ p u m p = m ˙ 5 h 5 - m ˙ 4 h 4 = m ˙ 5 (P 5 - P 4) ρ 5 η p u m p$
节流阀	$m ˙ 9 h 9 - m ˙ 8 h 8 = 0$ ; $m ˙ 13 h 13 - m ˙ 12 h 12 = 0$

Table 1 Energy conservation of system components

部件	能量守恒关系式
蒸发器	$Q ˙ e v a = m ˙ 1 h 1 - m ˙ 13 h 13 = m ˙ F 1 (h F 1 - h F 2)$
吸收器	$Q ˙ a b s = m ˙ 3 h 3 + m ˙ 9 h 9 - m ˙ 4 h 4 = m ˙ a b s, C 1 (h a b s, C 2 - h a b s, C 1)$
溶液换热器	$m ˙ 5 h 5 + m ˙ 7 h 7 - m ˙ 6 h 6 - m ˙ 8 h 8 = 0$ ; $η e x c = (t 7 - t 8) / (t 7 - t 5)$
发生器	$Q ˙ g e n = m ˙ 10 h 10 + m ˙ 7 h 7 - m ˙ 6 h 6 = m ˙ H 1 (h H 1 - h H 2)$
压缩机	$W ˙ c = m ˙ 3 h 3 - m ˙ 2 h 2 = m ˙ 2 (h 3, i - h 2) / η i$ ; $W ˙ e = W ˙ c / η e$
冷凝器	$Q ˙ c o n = m ˙ 10 h 10 - m ˙ 11 h 11 = m ˙ c o n, C 1 (h c o n, C 2 - h c o n, C 1)$
回热器	$m ˙ 11 h 11 + m ˙ 1 h 1 - m ˙ 12 h 12 - m ˙ 2 h 2 = 0$
溶液泵	$W ˙ p u m p = m ˙ 5 h 5 - m ˙ 4 h 4 = m ˙ 5 (P 5 - P 4) ρ 5 η p u m p$
节流阀	$m ˙ 9 h 9 - m ˙ 8 h 8 = 0$ ; $m ˙ 13 h 13 - m ˙ 12 h 12 = 0$

Fig.3 Model validation of single-effect and compression-absorption refrigeration system

Fig.4 Server utilization-energy consumption model

Table 2 Parameters in rated operating condition

工质	工况参数	状态点	设计值
冷却液	输入温度/℃	t_H1	60.00
冷却液	输出温度/℃	t_H2	56.00
空调冷水	输入温度/℃	t_F1	18.00
空调冷水	输出温度/℃	t_F2	12.00
溶液	发生器温度/℃	t₇	53.00
	吸收器温度/℃	t₄	32.00
	溶液换热器效率	η_exc	0.80
制冷剂	蒸发温度/℃	t₁	10.00
	冷凝温度/℃	t₃	32.00
	压缩机压缩比	CR	1.60
	压缩机等熵效率	η_i	0.70
	压缩机电效率	η_e	0.38
冷却水	输入温度/℃	t_C1	24.00
	吸收器温差/℃	t_abs,C2 - t_C1	5.00
	冷凝器温差/℃	t_con,C2 - t_C1	5.00

Fig.5 Influence of tF2 and tH1 on system performance

Fig.6 Influence of tC1 and CRon system performance

Fig.7 Distribution of average hourly temperature and humidity in Beijing in the past 30 years

Fig.8 Weekly distribution of wet bulb temperature and cooling water temperature in Beijing

Fig.9 Variation of operation parameters with CPU utilization

Fig.10 Operation characteristics of refrigeration with waste heat recovery of servers in high-power mode

Fig.11 Operation characteristics of refrigeration with waste heat recovery of servers in low-power mode

Fig.12 System performance in week No.31 and No.36

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