Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation
Electrocaloric Cooling Cycles in Lead Scandium Tantalate with True Regeneration via Field Variation
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DOI：
10.1103/physrevx.9.041002
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发表时间：
2019-10-02
影响因子：
12.5
通讯作者：
Mathur, N. D.
中科院分区：
文献类型：
--
作者：
Crossley, S.;Nair, B.;Mathur, N. D.
人们对基于材料的热泵越来越感兴趣，这些材料在相变由电场、磁场或应力场的变化驱动时显示出热变化。重要的是，再生允许通过材料本身可能产生的温度变化的许多倍来热分离散热器和负载。然而，性能和参数化受到热工作体和传热流体之间的净热传递的影响。在这里，我们表明，这种净转移可以避免，从而在真正的，平衡的再生，如果一个不同的施加电场，而电热（EC）的工作机构倾倒热量穿越被动流体回热器。我们的EC工作体是由散装PbSc0.5Ta0.5O3附近的一阶铁电相变，在那里我们记录直接测量的绝热温度变化高达2.2 K。间接测量的绝热温度变化类似的幅度被确定，不像正常的，从绝热测量极化，在附近的测量设定温度，而不假设一个恒定的热容。我们的材料的所得高分辨率场-温度-熵图和小的夹持伴随样品用于构建冷却循环，其假设使用理想的被动再生器，以便跨越50%的明确定义的效率，其不会被小的场滞后过度损害。我们的方法允许在被动再生器中的任何热量材料的限制性能被建立，优化和比较;提供了一个真正的再生在原型冷却装置的配方;并可以扩展到平衡主动再生。
There is growing interest in heat pumps based on materials that show thermal changes when phase transitions are driven by changes of electric, magnetic, or stress field. Importantly, regeneration permits sinks and loads to be thermally separated by many times the changes of temperature that can arise in the materials themselves. However, performance and parameterization are compromised by net heat transfer between caloric working bodies and heat-transfer fluids. Here, we show that this net transfer can be avoided-resulting in true, balanced regeneration-if one varies the applied electric field while an electrocaloric (EC) working body dumps heat on traversing a passive fluid regenerator. Our EC working body is represented by bulk PbSc0.5Ta0.5O3 near its first-order ferroelectric phase transition, where we record directly measured adiabatic temperature changes of up to 2.2 K. Indirectly measured adiabatic temperature changes of similar magnitude are identified, unlike normal, from adiabatic measurements of polarization, at nearby measurement set temperatures, without assuming a constant heat capacity. The resulting high-resolution field-temperature-entropy maps of our material, and a small clamped companion sample, are used to construct cooling cycles that assume the use of an ideal passive regenerator in order to span 50%) well-defined efficiencies that are not unduly compromised by a small field hysteresis. Our approach permits the limiting performance of any caloric material in a passive regenerator to be established, optimized, and compared; provides a recipe for true regeneration in prototype cooling devices; and could be extended to balance active regeneration.