Development of a Portable Adsorption-Based Medical Cooling Device

摘要

Therapeutic hypothermia is the process of cooling a post-cardiac arrest patient and reducing core temperature to approximately 33°C in order reduce long-term neurological damage. Recent studies have shown that cooling the patient earlier is better, however, current cooling devices available for use in transit (e.g. ambulance) are often too bulky, or are too primitive (e.g. ice packs). Consequently, a portable cooling device that does not require input power is needed for use in transit to the hospital. The current work evaluates the feasibility of a sorption-based portable device for this application. The main challenges include the high pressure drop inside the adsorbent bed, heat dissipation to the environment, and design of a flexible evaporator that is structurally stable at vacuum condition to allow vapor flow. A custom gravimetric apparatus was designed to evaluate potential sorbents and their performance at different temperatures. Experiments from the gravimetric apparatus showed an uptake of 10% within 60 min for silica gel loaded with 28% CaCl_2 at adsorbent temperature of 45 °C and evaporator temperature of 10 °C, proving that the amount of adsorbent required for this application is only around 3 kg. Subsequently, numerical simulations were conducted to analyze sensitivity of the performance to various adsorbent and design parameters. Results showed that improving heat loss from the adsorbent bed would significantly improve performance.