Ahmed Rezk

Experimental investigation of metal organic frameworks characteristics for water adsorption chillers

Adsorption cooling is a promising technology that can effectively utilise waste heat from many industrial processes for refrigeration and air conditioning. The choice of the adsorbent in this technology is vital to produce efficient and compact systems. Metal organic frameworks are new microporous materials with exceptionally high porosity and large surface area that can be used as adsorbents. This article experimentally investigates the characteristics of seven metal organic frameworks in terms of water adsorptivity compared to silica gel RD-2060. The adsorption characteristics were determined using an advanced gravimetric dynamic vapour sorption test facility. Results revealed that HKUST-1produced the highest water adsorption uptake with up to 95.7% increase compared to silica gel RD-2060 but showed deterioration in water adsorptivity with time. Throughout the temperature range tested, Fe-BTC has shown little hysteresis and produced up to 26.8% higher maximum water uptake value than silica gel RD-2060. These results highlight the potential of using certain metal organic frameworks materials to improve the efficiency of adsorption cooling systems; however, the thermal instability of some metal organic frameworks remains an issue that needs to be resolved.

Experimental and theoretical investigation of small-scale cooling system equipped with helically coiled evaporator and condenser

Utilizing helically coiled tubes evaporator and condenser in cooling applications is promising due to their higher heat transfer coefficients compared to straight tube because of the effect of centripetal forces. With growing interest in miniature and efficient refrigeration systems, small helical coil diameter can offer significant advantages in terms of being compact, lightweight, and improved coefficient of performance (COP). This article describes a performance study of small-scale vapour compression cooling system (100 W cooling capacity) equipped with shell and helically coiled tube evaporator and condenser. A detailed mathematical model has been developed for this system based on thermodynamic principles and relevant heat transfer correlations. The model was validated using experimental results from a representative small size cooling system with agreement of ±5 per cent. The model was then used to carry out performance optimization in terms of the evaporator and condenser geometric parameters including helical coil diameter, tube inside diameter, and surface area ratio. For the range of geometrical parameters investigated, the model predicts that as the coil diameter decreases, the Cooling COP improves.