Pradeep Bansal

Analysis of environmentally friendly refrigerant options for window air conditioners

This article presents a technical assessment of environmentally friendly refrigerants as alternatives to R410A for window air conditioners. The alternative refrigerants that are studied for its replacement include R32, a mixture of R32/R125 with 90%/10% molar concentration, R600a, R290, R1234yf, R1234ze, and R134a. Baseline experiments were performed on a window unit charged with R410A. The heat pump design model was modified and calibrated with the baseline data and was used to evaluate the comparative performance of the window air conditioner with alternative refrigerants. The article discusses the advantages and disadvantages of each refrigerant and their suitability for window air conditioners. Among all of the refrigerants studied, R32 offers the best efficiency improvement over R410A and has a 67.5% lower global warming potential.

Latest developments in not-in-kind refrigeration technologies

It is not surprising to note that the vapor compression refrigeration has consistently remained a predominant technology for well over a century. Although this technology offers advantages of good efficiency, satisfactory performance, and reasonable cost, it has a major weakness in terms of its environmental unfriendliness causing global warming. There is a growing concern that the increasing demand for heating, cooling, and refrigeration services world-wide may consequently lead to an increase in the related CO2 emissions. This trend could, however, be alleviated by the performance enhancement of current heat pumping technologies and/or the development of new energy efficient alternative technologies. There has been considerable effort in this area, where researchers (Bansal et al. 2012; Goetzler et al. 2014) have stressed the need for the development of efficient, low-cost, and not-in-kind refrigeration systems. There is, therefore, a strong need to develop not-in-kind technologies to replace conventional vapor compression refrigeration technology that can improve the energy efficiency and environmental friendliness of residential and commercial building equipment. Such technologies will be critical to provide energy savings or other environmental benefits for space conditioning, water heating, and refrigeration. This special section of Science and Technology for the Built Environment (STBE) presents selected high-quality articles in the field of next generation not-in-kind technologies for HVAC&R. Altogether, 10 articles made it into this special issue that cover a wide range of topics, including elastocaloric refrigeration (three articles), magneto-caloric refrigeration (five articles), Stirling cycle (one article), and compressor derived metal-hydride heat pumps (one article). Elastocaloric and magnetocaloric are the solid-state refrigeration technologies that avoid the use of “conventional” refrigerants with adverse global warming impact. Lately, materials having giant elastocaloric and magnetocaloric effect have underscored the potential for the fabrication of efficient refrigerators at room temperature. An ideal Stirling cooler is a reversed Stirling engine. Metal hydride systems operate using reversible adsorption and desorption of hydrogen from metallic compounds and can be incorporated in a cycle having a work input (compressor) or thermal energy input (generator). These technologies are still developing due to the current limitations posed by the state-of-the-art in materials research. A significant amount of research has recently been pursued in these areas where fast developments are occurring both in new materials and systems architecture. It is heartening to note that the future of these technologies is looking promising. Hold on to your seats and read on! Note: There is also a special bonus section of general interest articles.

The evolving science of ventilation, air conditioners, ground source heat pumps, and thermal comfort

The HVAC&R industry is going through significant transformation with new developments continuously occurring. All these developments are aimed at bringing in innovation with improved product quality and efficiency, and thereby better thermal comfort. This particular issue of Science and Technology of the Built Environment presents 10 technical articles to its readership that expand the science through specific contributions in ventilation, air conditioners, ground source heat pumps, and thermal comfort.

Advances in refrigeration and heat transfer engineering

This special edition of Science and Technology for the Built Environment (STBE) presents selected high quality papers that were presented at the 15th International Refrigeration and Air Conditioning Conference held at Purdue University during July 14-17 2014. All papers went through the additional review before being finally accepted for publication in this special issue of Science and Technology and the Built Environment. Altogether 20 papers made to this special issue that cover a wide range of topics, including advancements in alternative refrigerants, heat exchangers/heat transfer, nano-fluids, systems design and optimization and modeling approaches. Although CO2 may perhaps have been the most researched and popular refrigerant in the past decade, R32 is being seriously considered lately as an alternative and environmentally friendly refrigerant for small systems due to its low Global Warming Potential (GWP).

Preliminary Investigation of Novel Direct Contact Ultrasonic Fabric Drying

Thermal evaporation of moisture from clothes is the main technique used in clothes dryers today. Most of the energy supplied is spent to provide the latent heat of evaporation of water (2.5MJ/kg). This paper presents a novel direct contact ultrasonic system to mechanically remove water from wet fabric. The vibrations from the transducers are transferred by direct contact to the water inside the narrow pores of the clothes. Breaking the capillary adhesion of moisture at the interface between air and water allows water to exit the clothes as cold mist. The cold mist also carries with it most impurities such as minerals or detergents. This cannot be achieved in thermal dryers where water evaporates and leaves the impurities behind. Mechanical extraction of water is expected to be more efficient since thermal processing is not required. The majority of the supplied energy is used to mechanically separate water from the fabric. Initial testing has revealed that it is possible to dry a 1 cm2 piece of fabric from full saturation to a mere 0.4 % moisture content in just 14 seconds.Copyright