CO₂ Hydrates in Refrigeration Processes

Abstract

Global warming concerns have led the refrigeration industry to seek and develop new refrigeration systems with a reduced impact on the environment. The use of two-phase secondary refrigerants generated by a primary closed refrigeration circuit is a promising solution. Solidfluid secondary refrigerants are known for their higher energy efficiency compared to singlephase fluids, because of the additional latent heat of the solid phase. The objective of the present work is to investigate experimentally the latent heat of CO 2 hydrate-ice mixture systems in comparison to that of ice slurry systems. By using a new DTA apparatus, the CO 2 hydrate-ice mixture was shown to offer a dissociation enthalpy of 507 kJ/kg that is higher than that of ice (333 kJ/kg). Artificial tuned CO 2 hydrate-fluid systems appear to be an environment-friendly alternative for refrigeration and air-conditioning systems that can be used in a wide range of applications.

Influencing factors on the energy saving performance of battery storage and phase change cold storage in a PV cooling system

“…However, the full charge of battery cannot be 15 fulfilled within 8h when the sizing ratio exceeds a deflection point of 1.3. It is noted that this 16 deflection point appears after the sizing ratio exceeds 1, and the value depends on the PV panel sizing 17 and local solar radiation. 18…”

Pressure variation due to heat shock of CO2hydrate desserts

“…In addition to applications in CO 2 hydrate dessert packaging, the model developed here may be useful in design of two-phase secondary refrigerants containing gas hydrates for loops operating below $265 K. Several researchers have investigated gas hydrate slurries for secondary refrigerants, but typically only at temperatures of 265 K and warmer. 9,10 Gas hydrates are of interest because they can be formed by gas injection rather than mechanical processing and the latent heat of dissociation is the same order of magnitude as the latent heat of ice melting. At lower temperatures the latent heat of gas hydrate dissociation to ice and gas could provide improvements over use of a single phase working fluid.…”

Clathrate Hydrates for Thermal Energy Storage in Buildings: Overview of Proper Hydrate-Forming Compounds

“…Clathrate hydrates as PCMs have been mostly studied for cold storage in air conditioning systems [28][29][30]. Since this type of novel cold storage medium was first proposed, research activities have obtained outstanding achievements [31][32][33][34][35][36].…”

“…A compression cycle refrigeration unit (with a condenser installed outside the building) allowed, via a scraped surface heat exchanger (cooled down by the evaporator), the creation of TBAB hydrates slurries, which were stored in a tank during the night [36].…”