Basics on Air Conditioning VRS Refrigeration

BY MANUCHEHR MEHDIZADEH, BSME LIFE TIME MEMBER ASHRAE, COMMITTEE OFFICER @ IIR, REFRIGERATION CHAIR @ ASHRAE HOUSTON CHAPTER

Manuchehr Mehdizadeh

Before I discuss the impact of refrigeration (or cold chain) industries in our daily lives, it is imperative that we briefly discuss the status of air conditioning industries in our daily lives too.  It is ironic that both industries are covered by the principles of heat transfer system, where both follow Thermodynamic Principles, using the Psychrometric Chart to begin their heat load calculations, but yet these and other factors seem to be handled differently. 

The ‘R’ letter is a significant element of ASHRAE , where both are individual industries conforming to relevant ANSI/ASHRAE Standards & Codes ( particularly to Safety Standard 15), but it is interesting to note that , Refrigeration further follows applicable codes & standards set forth by ANSI approved IIAR of USA  supporting authoritative associations.  European countries in addition to ASHRAE, also tend to follow codes & standards set forth by UN/USNC-affiliated to IIR (located in Paris-France), maintaining strict support toward its other affiliated standards.  Also, in refrigeration system design works, we refer to Pressure-Enthalpy diagram and at times to Mollier Diagram (a variant of the Psychrometric Chart), a graphic representation of the relationship between air temperature, moisture content and enthalpy , and a basic design tool for building engineers & designers..  Too, It is  worth mentioning that during 2019, ASHRAE TC 1.6, Terminology, expanded its inside ASHRAE harmonization efforts by going outside ASHRAE for the first time. They worked with Refrigeration Subject Matter Experts (SMEs) from ASHRAE and the International Institute of Refrigeration (IIR) to create agreed-upon harmonized definitions for terms used by both IIR and ASHRAE.

As defined by ASHRAE, the human healthcare & comfort ‘Air Conditioning’ systems usually work a small, well-defined range of evaporating temperatures, typically 2C to 13C.  Because of these limited temperatures and the large market for air conditioning equipment, manufacturers can standardize their equipment and package it for volume production at lower cost.  While air conditioning system are highly recommended for human health & comfort, conversely the refrigeration system plays a more strategic role without which survival of modern world would be an issue. This is because refrigeration further plays a major role in today’s global economy with significant contributions towards food, health, thermal comfort, energy and environmental domains.

Furthermore, ASHRAE defines ‘Refrigeration’ as the process of moving heat from one location to another by use of refrigerant gas in a closed refrigeration cycle.   Oil management, gas & liquid separation, sub-cooling, superheating and piping of refrigerant liquid, gas and two-phase flow are all part of refrigeration.  Besides ammonia refrigeration also applies to air conditioning, commercial refrigeration.  IIR estimates that impact on climate change thru refrigeration sector account for approx. 20% on the overall electricity used worldwide and 10% of global greenhouse gas emissions.  Thus, the sustainable growth of refrigeration sector in the coming years is due to cooling needs in various fields of our lives and off course demand for decrease in global warming.  The Refrigeration industry supports various applications, extensively involved in chilling & freezing technologies.

Basically the functions of refrigeration systems are : a) to reduce the temp of substance- the act of cooling; b) to transform a substance (phase change function) from one state to another –as water to ice; c) to transform a substance from one state to another – as in the storage of ice or the preservation of food products.  The industrial refrigeration systems commonly operate 16-20 hrs. per day, as compared to perhaps 8-12 hrs. per day for air conditioning systems.  Generally component materials used on industrial refrigeration systems are heavy-duty industrial type, and when designed and installed correctly, remains durable for perhaps 30 to 40 years of its operation period, as compared to 18-22 years for air conditioning systems.

Besides in the refrigeration sector, it is not the volume of gas pumped nor the piston displacement of the compressor determines the amount of cooling performed. Rather the amount of cooling depends on the weight of the gas condensed and evaporated.  This would mean that the production of low temperature requires circulation of large quantities of low-pressure gas.  This is where the ‘natural’ choice  selecting ammonia refrigerant gas stands undisputed,  because its characteristics at 20F evaporating and 95F condensing temp , results on the liquid to vapor volume ratio (for say one TR) has been calculated at 1:238, which is by far the highest & the best ratio achieved as compared to other refrigerant gasses.

On the economic side, for 2018-19, IIR estimated that with 15 million people globally employed in the refrigeration sector, where it is debated that overall global sales of refrigeration equipment estimated to be over 180 Billion USD.  While the air conditioning & heat pump sector globally employs far more than 15 million people and its global sales during 2018-19 was estimated between 100 to 120 Billion USD. (Global Sales figure mentioned herein could be debatable).

It is also appropriate to add that since March 2020 the world has been held hostage to corona virus pandemic ; hence authorities must  focus on this devastating issue until a suitable vaccine is discovered.  In view of the same,  safety & security engineers and  industry authorities are to urgently introduce new regulatory requirements and help make changes on various building & facilities’ engineered systems & operations including industry codes & standards for ASHRAE , IIAR, NFPA, OSHA EPA etc. where all such changes have to accordingly be adjusted and strictly practiced.

Finally, it is imperative to mention that the ‘World Refrigeration Day’ takes place on every June 26th, celebrated as the national day of cooling – sort of coolest day of the year, also supported by ASHRAE & IIR.  This day celebrated as an opportunity on tremendous contributions that Refrigeration and Air Conditioning brings to our societies.

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