Influence of cold storage operation on its refrigeration system performance

Anil D Gulanikar, Immediate past President of Association of
Ammonia Refrigeration (AAR ) & Director of ammonia refrigeration consulting firm  “DAG-TECH-SERVICES” based out of Pune, India | Member of AAR, ASHRAE, & ISHRAE

Refrigeration systems are widely installed in India more than 60 years . We have developed knowhow and technology to manufacture refrigeration equipments in India. We also have world class design, engineering, installation and commissioning team & knowledge for refrigeration system.

Fortunately India has been using sustainable natural refrigerant “Ammonia” for over 100 years. Many refrigeration systems for cold storages and food processing industries installed are more than 20-35 years old. They were designed and installed with technology available during those days for cold chain industry in India since 1930.

All world leading brands on Ammonia refrigeration have their regional office or exclusive distributors in India. ‘Make in India’ equipment almost exist on major installations. Government supports has been fairly available. Hopefully Indian standards for refrigeration system design, Installation, & safety will be standardized.

India is contributing to ensure environmental safety. Knowledge & capability is available within India to conceptualize design, Install world class sustainable, energy efficient, safe, & simple to operate Industrial refrigeration system. In-house capability and knowledge are available to design and install fully automated plant year-round.

However some of the weakness of Indian cold chain industry such as on large  sectors, systems are not designed, installed, commissioned , operate and maintained by qualified persons; where priority is provided only on lowest initial investment, less awareness & lack of willingness to encourage industry safety  practices in refrigeration. Developers see the investment on safety as non-productive investment, lack of willingness to follow authorized applicable standards, creating SOP/ documents, HAZOP study and auditing compliance.  

Plants are installed and equipment are selected based on what others have executed without evaluating specific project requirements.  There seems lack of education, certification and training. Perception is investing on knowledge; training, developing skill are waste of time & money.

Commonly asked question by all concern is “Are the room temperature maintained properly?” if not then always blame is on refrigeration system and its team for non-achievement of required room temperature or the product parameters. 

In this article we will focus on external factors affecting performance in the refrigeration system, which begins with conceptualization stage of the facility.

To understand influencing factors on refrigeration system, we need to study and understand various categories of cold storages for food preservation, few of which are stated below.

  • CA storage for long term fruits and vegetables.
  • ACUs at temperature of 0℃ and above.
  • High temperature freezers at -2℃ to -3℃.
  • Low temperature rooms for general frozen product :-20 to -29℃
  • Low temperature storage at -20 to -29℃  with surplus of refrigeration product received at above -18℃

The refrigeration system is the main energy consumption source in the entire cold chain. A Typical refrigeration system consumes approx 75% of  total power requirement of cold storage impacting on operating cost as shown in Table: 1 below.

Pursuing the updated industry trend by digitalizing & automation, optimizes energy of refrigeration system and makes operation profitable.

There are various external factors which contribute to energy efficient trouble free refrigeration system. Some such areas which we need to concentrate on, are stated below:

  • Availability of power and water helps for uninterrupted operation and  better system performance.
  • Proper plant security prevents unauthorized persons entry and helps to prevents accidents.
  • Unplanned and delayed loading and unloading operation brings in continuous hot ambient, humid air inside dock and cold rooms affecting the temperatures maintenance of the product stored inside cold rooms. 10 to 12 hours of loading and unloading operation in a day can be considered as heavy loading whereas acceptable period is 4 hours.
  • Loading Docks should be temperature controlled designed to prevent hot ambient humid air entry during loading/unloading operation. As shown below , number of rapid opening dock doors with dock seal, dock levellers to be decided based on fast track product movement in a day.
  • Room dimension to be decided based on daily product intake and  specific customer requirements. Too large size rooms may affect temperature maintenance.

Proper product stacking system as shown below also helps to maintain desired temperature inside rooms, ensures proper air circulation and helps to achieve proper room temperature and product.

  • It is important to constantly monitor daily input being taken inside rooms along with inlet temperature of product w.r.t designed capacity of  rooms and inlet temperature of product. on both cases maintenance of room/product temperature are not possible to achieve.
  • Temperature Excursions – Temperature excursion is a deviation from given instructions. In case of certain product this term is commonly used when maintenance and recording of uniform product temperature is absolutely mandatory. It is defined in the WHO Model Guidance as “an excursion event in which Time Temperature Sensitive Pharmaceutical Product (TTSPP) is exposed to temperatures outside the range(s) prescribed for storage and/or transport. Temperature ranges for storage and transport may be the same or different; they are determined by the product manufacturer. Applicable for any product consumed by human being. Preparation and strictly following special System Operating Procedures(SOP) will help to achieve desired requirement. 
  • Proper layout as shown below of cold storage helps to achieve desired results from the refrigeration system.

The above sample layout shows proper location of plant room w.r.t. Cold rooms, location of Air Cooling Units (ACU), proper locations of other utilities such as charging station, entry of service persons, etc.

This avoids unauthorised entry and frequent entries inside the premises, avoiding frequent entry inside cold rooms for maintenance and operation, and in turn helps to maintain proper temperatures. Location of cold room w.r.t ante rooms and dock as shown above also helps to maintenance of desired room temperatures. Optimum traffic on material and manpower movement flow inside cold room also helps  achieving desired results. The number and size of cold rooms must be decided based on how much percentage of products are for rooms on chiller mode and those for freezing mode.

Initially when plant is new, we may not get clear picture about plant performance & operation related issues.

When plant operation reaches its maximum set limit then, plant operation related issues start affecting the performance of the refrigeration system and always blame is given to refrigeration system rather than looking into factors affecting performance of the refrigeration system.  

Facility owners normally provide more trust on keeping more and more production/storage / maintenance of temperature, rather than plant performance, its operation and maintenance and safety.

These results into non maintenance of desired temperature parameters, poor plant performance, rise in energy consumption, increase in running hours of compressors and increasing cases of breakdown along with rise in operating cost.

The recommended approach to overcome all above external factor affecting the refrigeration plant performance are as below:

  • Digitization of entire cold storage activity with remote monitoring  helps to monitor and control external factors affecting the refrigeration system performance.
  • Reduce human dependence as far as possible.
  • Create proper measures such as data recording , bar coding, tagging system , avoid human error and intervention
  • We should be able to monitor entire cold storage operation remotely.
  • Automation to be developed to help plant operator to obtain desired parameters.

To conclude following are salient points to remember:

  • For any cold chain operation, ensuring external factor affecting the desired refrigeration plant performance must be taken into account.
  • Thus optimization of OPEX, system reliability, safety & security, and rise  productivity together with improved working environment
  • Every year proper analysing and evaluating present operation by external expert will help to optimize the entire cold storage  operation.
  • While replacement of equipment if any, Optimize Capex along with Opex.

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