Mall Gita, Hubig Michael, Beier Gundolf, Büttner Andreas, Eisenmenger Wolfgang
Institute of Legal Medicine, University of Munich, Frauenlobstrasse 7a, 80337 Munich, Germany.
Leg Med (Tokyo). 2002 Jun;4(2):71-8. doi: 10.1016/s1344-6223(02)00005-6.
The temperature-based determination of the time since death in the early post-mortem (pm) period plays an important role in medico-legal practice. In contrast to the common opinion according to which convection and conduction are mainly responsible for post-mortem heat loss, a considerable part of energy is emitted by thermal radiation. The present paper concentrates on the heat loss due to radiation and natural convection. Since both heat transfer mechanisms depend on the temperature gradient between skin and environment, the skin temperature was measured in corpses of different constitution (lean, medium and obese) and its decrease fitted by a single-exponential model. Heat loss due to radiation was calculated according to the non-linearized form of the law of Stefan and Boltzmann, heat loss due to natural convection according to the semi-empirical thermodynamic laws; the shape of the body in supine position was approximated to a semi-cylinder of finite length. The power due to radiation ranged between 386kJ/h (lean) and 550kJ/h (obese), that due to natural convection between 307kJ/h (lean) and 429kJ/h (obese) initially. Cumulative energy loss amounted to 2167kJ (lean) and 4239kJ (obese) by radiation and 1485kJ (lean) and 2922kJ (obese) by natural convection up to 20h pm. The energy loss due to radiation plus natural convection initially exceeded the energy loss due the decrease of the energy content of the body (mass x heat capacity x temperature decrease). This surplus can be explained only by exothermal processes in the phase of intermediary life and directly provides lower bounds for supravital energy production. Cumulative supravital energy ranges between 1139kJ up to 5h pm in the lean and 2516kJ up to 10h pm in the obese corpses. The courses of supravital energies and powers are presented as functions of time. Under standard conditions like still air (no forced convection) and insulating ground (little conductive heat transfer), the lower bounds represent estimates for total supravital energy production.
在死后早期基于温度确定死亡时间在法医学实践中起着重要作用。与通常认为对流和传导是死后热量散失主要原因的观点不同，相当一部分能量是通过热辐射散发的。本文着重研究辐射和自然对流导致的热量散失。由于这两种热传递机制均取决于皮肤与环境之间的温度梯度，因此在不同体质（消瘦、中等和肥胖）的尸体上测量了皮肤温度，并通过单指数模型拟合其下降情况。根据斯蒂芬-玻尔兹曼定律的非线性形式计算辐射导致的热量散失，根据半经验热力学定律计算自然对流导致的热量散失；仰卧位人体形状近似为有限长度的半圆柱体。辐射功率最初在386kJ/h（消瘦）至550kJ/h（肥胖）之间，自然对流功率在307kJ/h（消瘦）至429kJ/h（肥胖）之间。直至死后20小时，辐射累积能量损失为2167kJ（消瘦）和4239kJ（肥胖），自然对流累积能量损失为1485kJ（消瘦）和2922kJ（肥胖）。辐射加自然对流导致的能量损失最初超过了由于尸体能量含量下降（质量×热容量×温度下降）导致的能量损失。这种过剩只能通过中间生命阶段的放热过程来解释，并直接给出了生前能量产生的下限。消瘦尸体生前累积能量在死后5小时内为1139kJ，肥胖尸体在死后10小时内为2516kJ。生前能量和功率的变化过程表示为时间的函数。在静止空气（无强制对流）和隔热地面（传导热传递少）等标准条件下，下限代表生前总能量产生的估计值。
