What is it about?

This study compares two liquid mixtures used in a special kind of heat pump that can cool or heat spaces by absorbing and releasing heat, like a reverse air conditioner powered by low-grade heat sources such as waste heat or solar energy. The standard mixture is water mixed with Lithium Bromide (LiBr), but it has problems like crystallizing (forming solids that block the system) at high concentrations or temperatures. The new mixture is water with three hydroxides—sodium (NaOH), potassium (KOH), and cesium (CsOH)—in a 40:36:24 ratio. Using computer models, the researchers calculated efficiency (COP, or output heat divided by the total input heat), flow rates of the liquids, and how temperatures affect performance in both cooling (e.g., for air conditioning) and heating modes (e.g., for hot water). Key conditions: generator heats up to 75-105°C (167-221°F), evaporator cools to 2-6°C (36-43°F), and condenser/absorber rejects heat at 30-40°C (86-104°F). Results show both mixtures have similar efficiencies (COP around 0.5-0.8), but the hydroxide one works at higher temperatures without crystallizing, making it easier to use air for cooling instead of water. It's like upgrading a fridge to handle tougher conditions without breaking down, potentially saving energy in buildings or industries.

Featured Image

Why is it important?

In 2025, with energy crises and climate goals pushing for efficient heating/cooling (responsible for 50% of global energy use), this 2001 research is key for sustainable tech like absorption pumps that reuse waste heat, cutting fossil fuel reliance by 30-50%. Unique is the ternary hydroxide's edge over LiBr: no crystallization at high temps/concentrations, enabling air-cooling (cheaper, water-saving), higher temperature lifts (up to 40°C more), and broader applications in hot climates or industries. It could lower costs (e.g., 20% less maintenance) and emissions, especially in developing areas with solar/waste heat. With 36 citations, it has spurred alternatives to toxic LiBr, influencing modern hybrids with renewables, boosting adoption in Europe/Asia for net-zero buildings.

Perspectives

This paper in Applied Thermal Engineering Journal. compares an Absorption Heat Pump (AHP) for cooling/heating using H2O/LiBr versus an aqueous ternary hydroxide (NaOH:KOH:CsOH, 40:36:24 wt.%). The AHP upgrades low-grade heat (e.g., 75-105°C generator) to useful levels, with evaporator at 2-6°C for cooling or the higher device part for heating, condenser/absorber at 30-40°C. For the calculations, several assumptions were made: steady-state, mass/energy/concentration balances, Gibbs phase rule for saturation, and negligible pump work. Thermophysical properties (vapor pressure, density, viscosity, specific heat) for ternary from measurements (e.g., solubility 277-431 K).

Professor Rosenberg J Romero
Universidad Autonoma del Estado de Morelos

Read the Original

This page is a summary of: Theoretical comparison of performance of an absorption heat pump system for cooling and heating operating with an aqueous ternary hydroxide and water/lithium bromide, Applied Thermal Engineering, August 2001, Elsevier,
DOI: 10.1016/s1359-4311(00)00111-3.
You can read the full text:

Read

Contributors

The following have contributed to this page