Forced-flow thermocells that generate electric power during cooling
Forced-flow thermocells that generate electric power during cooling
复制标题
在冷却过程中产生电力的强制流动热电池
DOI：
10.11470/jsaprev.230408
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发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Yutaka Ikeda
中科院分区：
文献类型：
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作者：
Yoichi Murakami;Yutaka Ikeda
电子设备和热力发动机分别消耗电力和燃料，产生和排出热量。这样的发热源通常通过强制对流冷却来冷却，其中流体流过待由泵冷却的物体。强制流动液体冷却已被用于功率半导体[1]，数据中心的CPU [2]和电动汽车电池[3]。因为热是一种能量，不利用产生的热量被认为是机会的损失。然而，重要的是要注意，这种类型的热量是麻烦的废热，而不是丢弃（或废弃）的热量。例如，后者是从发电厂喷出的温暖的二次冷却水中提取的热量;这些热量可以在离开其产生的位置后自由利用[4]。图1（a）示出了散热物体的表面（在温度TH（K）下）和用于冷却它的冷却剂的流动（在混合平均温度TL（K）下）。在这里，以Etherm（J）表示每1 s在物体中产生的热能，并假设稳定状态，Q= Etherm（J）的热量每1 s从热物体传递到冷却剂（注意“热能”和“热量”之间的区别[5]）。热能在这种传递过程中被保存。然而，在图1（a）所示的情况下，由于温度的降低，热能的有效能[5]不可逆地减少;在初始状态下使用TH处的Etherm可以比在最终状态下使用TL处的Etherm产生更多的功。这可以看作是一种情况，其中水轮没有安装，即使有瀑布。以前，这一点没有得到解决，因为它隐藏在冷却的紧迫性后面。值得注意的是，将热电板插入固体（待冷却的热物体）-液体（冷却剂）界面并不产生预期的结果[4]。这是因为在固体表面上流动的流体的热边界层中，最大的温度降通常发生在通过其传递热量的固液界面附近。换句话说，热源和环境之间的最大温降发生在热边界层上，热边界层通常具有最大的热阻，而不是热电板[4]。这是所提出的技术概念的基础。
Electronic devices and heat engines consume electricity and fuel, respectively, which generates and exhausts heat. Such heat generation sources are often cooled by forced convection cooling, in which a fluid flows over an object to be cooled by a pump. Forced-flow liquid cooling has been adopted for power semiconductors [1], CPUs in data centers [2], and electric vehicle batteries [3]. Because heat is a kind of energy, not utilizing the generated heat is considered a loss of opportunity. However, it is important to note that this type of heat is troublesome exhaust heat rather than discarded (or abandoned) heat. The latter is, for example, heat extractable from warm secondary cooling water ejected from a power plant; such heat can be utilized freely after it leaves the location where it is generated [4]. Figure 1 (a) shows the surface of a heat-dissipating object (at temperature TH (K)) and the flow of the coolant used to cool it (at a mixed-mean temperature TL (K)). Here, denoting the thermal energy generated in the object per 1 s by Etherm (J) and assuming a steady state, the heat of Q= Etherm (J) is being transferred from the hot object to the coolant per 1 s (note the difference between “thermal energy” and “heat”[5]). Thermal energy is conserved during this transfer. However, in the situation shown in Fig. 1 (a), the exergy [5] of the thermal energy is irreversibly reduced owing to the decrease in temperature; more work could be generated using Etherm at TH in the initial state than using Etherm at TL in the final state. This can be regarded as a situation in which a water wheel is not installed even though there is a water fall. Previously, this point was not addressed because it was hidden behind the urgency of cooling.Notably, the insertion of a thermoelectric plate into a solid (hot object to be cooled)–liquid (coolant) interface does not yield the intended consequence [4]. This is because near the solid–liquid interface, through which heat is transferred, the largest temperature drop usually occurs in the thermal boundary layer in the fluid flowing on the solid surface. In other words, the greatest temperature drop between the heat source and environment occurs across the thermal boundary layer, which usually has the largest thermal resistance, rather than across the thermoelectric plate [4]. This is the basis of the concept of the proposed technology.