Numerical analysis of heat and mass transfer processes within an infant radiant warmer

• Main Author: Duda, Anna
• Published: University of Leeds 2011
• Subjects: 618.9201
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.555901

An optimal thermal environment is regarded as a priority in the medical care of newborn infants (neonatology). Survival of each neonate (newborn infant) depends on the ability to regulate its temperature. Preterm and small neonates often cannot respond to the environmental temperature changes. For this reason, maintenance of neonates bodies within a narrow temperature range is essential for their survival and growth. However, there is one major concern when using radiant warmers, namely the neonates often become severely dehydrated when nursed in these devices. For this reason, the major objective of this thesis is to find a solution to this difficulty. In order to achieve this goal, numerical techniques including Computational Fluid Dynamics and conjugate heat transfer were employed. Mathematical mod- els applied to living organisms can provide a better understanding of the thermal processes occurring i~side a human body, together with their interactions with the surrounding environment. Therefore, in this thesis we focus on developing a model of a neonate under a radiant warmer that incorporates both heat and mass transfer processes in order to provide a better understanding of how a radiative heat source interacts with a neonate. The numerical models were prepared in ANSYS FLUENT and ANSYS CFX commercial softwares. The flow was assumed to be turbulent, and radiation cal- culations were performed as they are a crucial part of this analysis. Moreover, a semi-analytical ray tracking method was developed for the purpose of validating the numerical results. A good general agreement was observed when comparing the ray tracking results with the numerical ones. Next, a heat generation within the newborn was considered, and the numerical data was validated against the analytical calculations, and this comparison showed a good agreement of the results obtained using these two different techniques. Finally, several modifications to the geometry and operation of the radiant warmer are introduced in order to assist with the difficulty of high temperature gradients being obtained on the skin of the newborns nursed under the radiant warmer. It was found that the proposed modifications reduce the large temperature differences on the skin of the newborn. A more uniform temperature field on the skin will result in decreasing the evaporative loss. The proposed modifications in- clude to different approaches. Namely, the first solution, being a high conductivity blanket, can be easily implemented by the staff of the hospital. The second solution introduces modifications to the design of the radiant warmer, and it could be of interest to the producer of the device. Therefore, the main goal of this project, namely to find a solution to newborns becoming dehydrated when nursed under radiant warmers, has been successfully achieved.