I II IT I

Cenf m repot= Comptes-rendus de conferences

III IIII IIII I I II I I ! IIIIIIII I

1981 ASHRAE semi-annual meeting Chicago, Illinois, USA, January 25-29 1981

The 1981 semi-annual meeting of the American Society of Heating, Refrigerating and Air- Conditioning Engineers Inc. (ASHRAE) held in Chicago was a great success. Short reports of some of the more in terest ing sessions at the ASHRAE meeting are given here.

Advances in food refrigeration

applicable to tuna in the Pacific and pollock, cod and flounder in the Atlantic and the Pacific. There are opportunities for vastly increasing frozen salmon, since the catch season lasts only three weeks, during which canning facilities are overtaxed. The shrimp fishery in the Gulf of Mexico requires improvement. At this time, shrimp boats use one gallon of fuel to catch 1 Ib (0.454 kg) of shrimp.

The first speaker, J. W. Slavin, discussed US fisheries. Slavin indicated that the total world fish catch by the year 2000 is expected to reach 100 million metric tons, which is probably more than can be caught by the current methods. It can, therefore, be expected that a substantial quantity of fish meal which is now nearly 30% of the total catch, will be c o n v e r t e d to more direct human food. Aquaculture can be expected to multiply probably 5- to 6-fold by the year 2000.

The 200 mile limit, which is now the international rule, simply gives each country the first opportunity to fish in its o w n waters. However, fishing vessels from other countries may be licenced. This is the case in US waters, particularly in the North Atlantic. In the Pacific, on the other hand, US vessels require licences from other countries. For the above and other reasons, 30% of the world fish catch moves in international trade with Canada being the largest exporter (about $1.2 billion) and the US a close second, with an annual export of $1 billion, but import of approximately the same size. (The major US import is frozen shrimp and tuna.) Japan is by far the largest importer of fish despite its own very large catch. Latin American exports are also very substantial, but consist mainly of fish meal.

Of the present world catch of 50 million metric tons, two-thirds are frozen. In the US, 60% of the fish are fresh-frozen. Per capita consumption is greates in China, Japan, the Soviet Union, and the US, in that descending order, with the US per capita consumption increased recently to 13 Ib (5.9 kg).

Recent studies indicate that US production could rapidly double from 3 to 6 million metric tons which would provide an additional 40000 jobs and $1 billion income. In order to do this, much of the fishing fleet would need to be replaced and expanded with larger fishing vessels which can process and freeze fish at sea. This is particularly

Slavin completed his presentation by emphasizing the need for improving the use of under-utilized species such as squid, herring and menhaden which are currently used largely for less valuable feed and fertilizer, but by appropriate technology could be used for food.

During the discussion which followed, it was emphasised that labelling restrictions, particularly in relation to species that may or may not be considered as tuna, are now being clarified by the International Codex Alimentarius so that Bonito will be included. Leading US exports are salmon and crab, while imports are tuna and shrimp. The major technologies needed by the US are on-board freezing and improved packaging. As to depletion of fish, most countries have already implemented fish conservation measures which are beginning to show their effect, so that a steady annual world catch of 70 million metric tons is assured, and may increase, to 100 million metric tons in the next decade. Aquaculture is already supplying up to 10% of the world fisheries, and is expanding into such species as sole, halibut and scallops.

Marvin Kahn, the inventor of the 'freeze-flow' process, presented this technique which is a means of storing products at about 0°F (-18°C) without going through a change of phase from liquid to solid. He emphasized that by avoiding the actual freezing of many products, there can be a substantial energy saving. For example, it takes only 5 Btu (5.28 k J) to reduce the temperature of many foods from 40 to 30°F (+5 to -1°C) and an additional 15 Btu (1 5.84 k J) to reduce temperatures after freezing to 0°F (-18°C). But 144 Btu (151.93 k J) are required to pass through the latent zone. Whenever actual freezing is avoided, 144 Btu (1 51.93 k J) of the total of 164 Btu (1 73.03 k J) can be saved. Kahn indicated that many formulated products which had been frozen in the past, can, by proper reformulation which binds much of the

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water, be stored at freezer temperatures without actually being frozen. He agreed that perhaps the freeze part of the freeze-flow name may be misleading since the entire objective of the technique is not to freeze. He then proceeded to suggest that entire food units such as strawberries or sliced apples can be handled by freeze-flow methods without the use of additives. These comments raised some questions resulting in the conclusion that some high moisture products, tomatoes for example, are definitely not suitable for freeze-flow. As for strawberries and similar products, Kahn suggested that certain sugars, such as fructose, bind water and therefore keep it from freezing much more effectively than other sugars. The same is true with fats where the unsaturated fats are more effective than the saturated fats. This led to the idea that certain sugars, fats, and other solids may be added to the natural product, or that naturally occurring substances can be converted to more highly water binding substances by the use of appropriate enzymes. In general, it appeared that the opportunity for producing products that remain unfrozen at freezer temperatures rests entirely on the formulation which reduces water activity sufficiently.

Some interesting comments made by participants from Japan and India, indicated that certain popular fish products (eg, imitation crab legs) and fruits (mangoes in honey) could be held in a freezer without freezing.

Kotula of the USDA Meat Science Research Laboratory, Beltsville, presented the next paper emphasizing the problems that US exporters of variety meats are now facing because of the poor quality of the frozen product exported from the United States. The problems can all be solved, but require new methods for freezing and packaging. Tongues, for example, are frequently discoloured and show signs of freezer burn which can be practically eliminated by vacuum packaging before freezing. Livers can be frozen too fast causing 'case hardening' which results in a green discolouration in the centres. Shipping in a controlled atmosphere can be very helpful. In fact, kidneys carefully packaged in a controlled atmosphere arrived in Europe in a satisfactory condition when they were not frozen, but just chilled to -1°C. He summarized the problem of export of frozen variety meats as follows: case hardening - freezing too rapidly; freezer burn - inadequate packaging; not individually quick frozen - buyer must thaw entire box; excessive drip loss; and unsightly boxes. Kotula emphasized that there are too many shipments suffering from the above defects, which end up as dog food.

Kotula then reviewed two recent developments in the handling of meat which could bring about substantial savings, increase total utilization, and improve quality and extend shelf life. These are hot boning and electric stimulation. In order to obtain a tender meat product, it is now necessary to allow the slaughtered carcass to go through rigor before further processing, freezing and packaging. If the muscle is frozen while it is still in rigor, it shrinks

and remains tough after it is frozen and prepared for consumption. With the current emphasis on less fat, this problem is more serious. When the muscle goes through rigor and the pH gets down to about 5.5, there is little contraction, and after freezing and cooking, the muscle retains its tenderness. If the unchilled carcass is boned while still warm (hot boning), a maximum amount of meat can be separated from the bones and the carcass can then be mechanically deboned with the mechanically deboned product handled very promptly so that its shelf life can be extended substantially. The deboned meat will also retain its tenderness if it is submitted to electrical stimulation. Hot boning plus electric stimulation may provide the break-through for central consumer-size cutting, packing and freezing of meat.

de Figueiredo, Ralston Purina, presented the final paper of the seminar discussing the future of frozen prepared foods. He stated that the 1980's present a challenge to those involved in the manufacture and sale of frozen prepared foods which, until recently, were accepted as being the best possible quality of any prepared foods. The current challenge comes from new methods of packaging, such as retortable pouches, which claim to be equal or superior to the frozen method, and substantially less energy intensive, de Figueiredo mentioned a number of long-term storage studies, all indicating that prepared frozen foods, if properly prepared, can be decidedly superior in quality to the equivalent canned retortable product unless the canned product is stored at low temperatures.

He emphasized, however, that there is the constant need for more efficient use of energy, improved product stability, and cost effectiveness. Government regulations, particularly in the area of food safety, will continue to be of importance in the manufacture and sale of frozen products prepared without the use of additives.

The ensuing discussion centred about the relative cost of energy of frozen vs canned vs raw food products. The conclusions drawn were that under current technology, energy costs for canning, freezing, or raw product distribution are remarkably similar when considering total costs from time of harvest (or slaughter) until the food reaches the consumer's table. In fact, the freezing process has a small lead. Comparing frozen to raw foods, the advantage is decidedly with the frozen foods for those commodities where not more than 50% is actually consumed. The challenge from the canned product is the new packaging - the retort pouch - which requires less energy in its manufacture and thermal process than the rigid cylindrical can. Despite numerous claims of energy savings of 40- 60% with the retort pouch, when spread across the entire marketing channel, the energy saving is reduced to about 6% when compared to frozen products. Equal or greater savings can readily be made in the handling of frozen products during retail distribution and in home storage.

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A second meeting, chaired by Symons, AFFI, was held in which members from IIR, ASHRAE, ARI and TRRF participated. Symons indicated that there are now very serious problems in connection with standards for refrigeration, particularly in international transportation, where importing countries may refuse refrigerated or frozen shipments simply because they do not have a sticker or label indicating that the shipment has conformed to certain international standards, even if the national standards to which the shipment conformed are far more stringent. An example was provided by Sealand Industries who described the standards which they had initially set up for containers to a length of 35 ft (10.67 m). Although 80% of all containers used in international commerce are of those specifications, shipments to Brazil were rejected because the size of the containers did not conform to more recent international standards requiring container to be 10, 20, 30 or 40 ft (3.05, 6.10, 9.15 or 12.20 m) long. This standard was adopted at the 1976 convention on standards for refrigerated and frozen foods. Since then the 35 ft (10.67 m) container was stopped in Europe as well as in some South American countries.

Heat recovery applications in the industrial refrigeration environment

The first speaker, K. O. Faber, discussed heat recovery techniques in grocery/coldstorage distribution centres. The system used by the author's company was one in which heat reclaim condensers were piped in parallel with the existing condensers. The head pressure was maintained by cycling fans in conjunction with liquid ammonia flooding the condensers. Two warehouses, one situated in Wisconsin, and the other in Michigan, were cited as case histories. However, since the Michigan warehouse was completed recently, not much data was available on it.

The heat reclaimed was used to heat the dry dock area, and to provide heat for underfloor heating of the frozen food warehouse. The tax credit of approximately $1 8000.00 helped to provide an additional incentive although a saving of $20000 per year (based on a heating oil cost of $0.45 per US gallon) was somewhat off-set by the one-time extra cost of $22 000 for installing the reclaim condensers.

R. A. Hall then spoke on heat recovery techniques chemical process refrigeration. He urged the refrigeration engineers to look for petrochemical process streams to reduce energy required for refrigeration. Three case histories were discussed.

Propane (R 290) had been used very successfully in a two-stage system without desuperheating by bubbling through a bubble type cooler/ desuperheater between stages, because it has low discharge superheat characteristics. The total BHP saving was 60 BHP, using a flash type intercooler and a process stream to provide further subcooling. The payback period was discussed. The

quotations are being estimated at $4000 per kW in USA and, therefore, any reduction in energy looked attractive.

A process stream was heated using the superheat from the refrigerant. In this process plant before the installation of new refrigeration equipment, the heat was provided by low pressure steam. The water available on this site was polluted, and the cost of treated water was Sl .25/1000 gallons, This new system saved $1 5 928.00 in the evaluation.

A stream of water-saturated hydrocarbon gas (at 240 psig) had to be cooled from 120°F (48.9°C) to +40°F (4.4°C), the dew point of the hydrocarbon gas. The non-condensable gases and the small amount of hydrocarbon still in the waste vent gases were used to cool the incoming original mixture of hydrocarbon and non-condensable gases. This additional heat exchanger gave gases an entering temperature into the normal gas chiller of 79°F (26.1°C) instead of 120°F (48.9°C) thereby reducing the refrigeration requirements tremendously.

B. E. Woods then discussed applied heat recovery in a meat packing plant. In a mean processing plant large quantities of hot water are required, and this can be heated using reclaimed waste heat. Typical processes with available waste heat are refrigeration rendering heat recovery and hog singeing heat recovery.

Desuperheaters (1 6 " x 1 4') were installed in the refrigeration system to reclaim heat from ammonia at 250-200°F (1 21.1-93.3°C) while heating water from 77°F to 95°F (25-35°C) and recovering some t 6 x 1 0 6 Btu day -1 (0.1954x106 J s- l ) .

The integrated heat recovery system heats a 23 000 gallon tank of water from 77°F to 140°F (25-60°C). The tax credit and the savings made the payback period 3-6 months to 3 years depending upon the investment. The compressor jacket heat recovery heated water to the boiler feed in one of the plants providing 40 x 106 Btu day -1 (0.488 x 106 J s -1) providing a saving of $30000 per year. The problem of available heat time not coinciding with the peak water demand was discussed.

F. M. Waiters then discussed energy saving by air cycle refrigeration and heating. The system used by the author's company is similar to the Boot strap cycle heating and cooling used in aircraft. Heat is reclaimed from the compressed air on its way from the low stage centrifugal compressor to the high stage centrifugal compressor. The heat available is at a temperature of approximately 600°F (31 5.6°C) and, therefore, can be used for such processes as blanching, drying or generation of low pressure steam. The 'high stage' centrifugal compressor is driven by a turbo expander which is not affected by dust, condensation or moisture, and has a high efficiency. The systems can be 200 hp (1 49.t4 kW) to 5000 hp (3728.5 kW). There is BHP saving when compared to a conventional refrigeration cycle. The freezing tunnel retention time of products to be

228 International Journal of Refrigeratior

fr{,zen is reduced by 30-40% thereby saving money. The author stated that heating COP wi l l be 2.3 and indicated that the systems were safe and reliable, and had low maintenance. The working fluid (air) is free.

Chlorofluorocarbons (CFC's): toward a balanced approach

I travelled back in time this past January, back to governmental hearings on DDT, but only for a short while. The occasion was an ASHRAE meeting in Chicago. Mr Douglas Kenna of the 'All iance for Responsible CFC Policy' recommended wait ing for ' incontrovertible evidence' before regulating usage of this 'beriign family' of chemicals by an 'essential' industry. Al though the top icwas chloro- f luorocarbons (CFC's), I felt as if I were again watching a chemical company apologist describing DDT.

A good case can be made for cautious limited application of pesticides. However, the 'business as usual' approach of the chemical companies to pesticide contamination led ,to severe regulation of this 'benign family' in some nations. It is time for users and manufacturers of CFC's to step out from behind our codewords and face our civic responsibilities.

For a number of years, scientists have known that CFC's can break down ozone under condit ions which exist in the upper atmosphere. We also know that CFC's slowly migrate up to the ozone layer, and that the ozone layer plays an important role in shaping the Earth's climate.

Unfortunately, no clearcut evidence exists as to what effect CFC's wil l have upon the ozone layer and, consequently, upon the Earth's climate patterns. CFC's take decades to migrate from the lower levels of the atmosphere to the stratosphere where they affect the ozone layer. Only a very small fraction (perhaps 1%) of the CFC's released thus far have reached the stratosphere. Natural cycles of ozone depletion and manufacture may have long periods and/or major variations in value. Measurement is therefore difficult, whi le analysis of the measurements is even more inexact.

The stable nature of CFC's in the lower atmosphere, the characteristic which gives them much of the commercial value, is possibly its worse detractor. Al though CFC's take decades to reach the stratosphere, virtually all those released at ground level do reach the stratosphere.

As a society, we cannot afford to wait for ' incontrovertible evidence' as Mr Kenna suggests. We are learning from our experiences with DDT and numerous other chemical contaminants that such a luxury is too dangerous for our children if not for ourselves.

Some compromise and caution on the part of industrial users of CFC's is appropriate at this time

rather than (hypothetical ly) after we have irreversibly contaminated the atmosphere.

Of course, we should voluntari ly restrict our usage of CFC's, and we should use the CFC's which have the least potential for ozone destruction. We should also welcome disincentives which would discourage our competitors and neighbours from using CFC's as well as other substances known to break down ozone, such as nitrogen based fertilizers.

A substantial excise tax on the manufacture of CFC's and other substances which break down ozone under stratospheric condit ions would probably be the fairest and simplest type of disincentive. This excise tax could be adjusted from year to year to limit usage of CFC's to a preset amount. International agreements to equalize this tax among nations could prevent any unwarranted shift in trade balances.

The American Environmental Protection Agency has proposed that the right to use CFC's be auctioned off to the highest bidders. This scheme seems unnecessarily complicated and harsh upon small users.

A substantial excise tax would disrupt the economy least. Adequate substitutes exist for many current users and many more can be made commercially feasible for others. This excise would al low consumers to decide how 'essential' their use is.

As a society we have to assign values to goods which reflect the costs which the use of the goods have upon society as a whole as,well as the cost of production. Artif icially low prices are often cited as the primary cause of America's profligate consumption of oil.

'Essential' is a shift ing concept. What is deemed essential today may not be so tomorrow. A growing consumption of oil was once thought to be essential to the health of the world economy. We should act now to assure our children of one essential: a healthy planet.

Contaminant problems in heat pump systems

Heat pumps are more likely to be damaged by contaminants than units employed only for air condit ioning because: hours of operation are increased, operating stresses cover a broader range, refrigerant f low is usually bi-directional, there are more components, reliability is lower, serviceability is poorer, and compromises are required in the design. For example, excessive moisture causes freeze up at the expansion valve, enters into acid formation, causes desiccant decomposit ion, sludge formation, and embritt lement of insulation. Control l ing contaminants requires the attention and co-operation of the manufacturer, installer, and servicer.

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The filter-drier is the main tool used for contaminant removal on heat pump systems. The fi lter-drier is applied in various ways as follows: two standard driers ahead of the expansion devices, two driers in the outdoor section, one drier, two drier-check valve assemblies, or a reversible filter-drier. The latter is particularly popular wi th servicemen because of its ease of installation.

Most driers do not have a filter at the inlet end. Therefore, if reverse f low occurs some desiccant particles can escape out of the inlet end. For this reason the drier should be piped in a horizontal, or preferably vertical downf low position. Procedures for clean up after a hermetic motor burnout are similar to the procedures generally used in air condit ioning systems.

In addition to the normal l iquid line application, it may be desirable to apply a fi lter-drier in the suction line or discharge line location. Both locations have some appeal because the refrigerant always flows in the same direction through these particular lines on a heat pump.

The higher velocity in the suction line requires a larger drier to keep the pressure drop wi th in acceptable limits. This location is frequently used for clean up after a hermetic motor burnout. Testing in the discharge line has demonstrated that a drier containing an all molecular sieve wil l retain at least 50% of its water capacity at the high temperatures involved. The discharge line location is not generally selected for drier application. Considerable study, and perhaps testing, is required before a drier can be selected for use in this location.

Industrial heat pump systems

The industrial sector uses about 36% of the total energy consumed in the United States. Much of this heat is ultimately rejected, after extraction of useful work, at temperatures below 1 50°F (65°C). Heat pumps, using industrial waste heat as a source, therefore offer strong potential for energy conservation. This report is a summary of a seminar that focused on developments in industrial heat pump technology, application of heat pumps to supply heat for industrial processes, and use of heat pumps for industrial waste heat for other beneficial uses. The systems discussed demonstrate that industrial heat pumps can conserve energy, be environmentally attractive, and reduce costs.

Heat recovery wi th high temperature heat pumps was discussed by R. C. Niess. The high temperature heat pump has been used to recycle waste heat in many commercial, institutional, and industrial applications. It has been linked with solar systems to make them more efficient and can enable greater use of geothermal resources. Heat pumps have been applied in a broad spectrum of industrial processes, where great potential for energy-saving heat recovery systems exist. Three typical installations were described. These included a meat packing

facility, a tractor manufacturing plant, and a sewage treatment plant. Coefficients of performance from 3.0-7.0 were obtained, wi th an average of 4.5, depending on the leaving temperatures of the hot water produced and the source water. The heat pumps involved employ both reciprocating and centrifugal compressors in rankine cycles using either R 12 or R 114.

A number of other plants and factories are now using similar heat pumps to economically recycle normally wasted heat generated by various processes. The result has been increased efficiency and a substantial saving in energy. Each of these heat recovery systems has been justified on a purely economic basis. Reduction of thermal emissions and avoidance of alternative combustion products result in favourable environmental benefits as well.

H. M. Liebowitz then evaluated industrial heat pumps for effective low-temperature heat use. The implementation of industrial heat pumps using waste water from various industrial processes for the production of process steam can be a viable economic alternative to conventional fossil-fired boilers and an effective fuel conservation measure. With advanced, high-performance industrial turbocompressors, waste stream temperatures as low as 140°F (60°C) can be used economically. Three heat pump systems, differing primarily in the heat exchange strategy from the effluent to the heat pump refrigerant, were presented. These included two detailed studies of open rankine cycle systems using water vapour as both the heat pump and process fluid. The heat pump costs, including amortization of the investment capital, maintenance, and electric power, compared favourably with conventional fossil-fuel-generated steam costs. The heat pump capacities involved ranges from 1 0 0 0 0 - 250000 Ib h -1 (3-70 MW) of process steam. System variables such as the waste steam temperature, process temperature, heat exchanger, and approach temperature were evaluated.

The vapours turbo-compressor used are high- performance units. Isentropic efficiencies of 80% at 45000 ft (135 MPa) can be obtained using a centrifugal impeller driven through a geared speed increaser. Tip speeds of up to 1500 ft s -1 (460 m s -1) at rotational speeds of 52000 rpm are characteristic of the compressors involved.

B. S. V. Setty then discussed the application of heat pump dehumidif ication in laboratories, hospitals, and industrial plants. The cost and energy savings of heat pump dehumidif ication, wi th double duct variable volume systems, desiccant systems, and humidif ication systems were highl ighted with particular discussion given to laboratory and industrial applications.

The dessicants used include l ithium chromide, l i thium chloride, and silica gel. Regeneration of the dessicants wi th heat from heat pumps has been found to be very cost-effective and allows concurrent cooling, thereby eliminating the need to

230 Revue Internationale du Froid

overcool and reheat. Supplementary heat sources used include solar energy, groundwater, and city (stored) water.

Industrial heat recovery applications was discussed by H. J. Kroll. Heat pumps can be applied to effectively use heat from various sources now being wasted in industrial processes. Representative applications include use of heat recovered from process cooling to heat factory and other building spaces, quench tank cooling with use of rejected heat in winter, simultaneous heating and cooling in a fraction column for distillation and product refinement. Five retrofit projects were discussed. These systems use heat recovery that has been overlooked in the past, but is now viable due to increased power costs and increased interest in conserving energy.

Dr G. Grossman then described absorption heat pumps for upgrading waste heat. This presentation described a heat pump cycle designed for upgrading low temperature waste heat by boosting its

temperature, typically from 1 40-220°F (60-105°C). The heat, which may be available from a variety of sources, is thereby elevated to useful temperatures for industrial and other applications. An absorption cycle for this purpose, which uses part of the low temperature heat as its source of energy, has been studied. An absorber/evaporator combination is employed to flash-evaporate some of the hot water and absorb the vapour in a concentrated absorbent solution; the heat of absorption is used to raise the temperature of another stream of water. Two stages of the above system are used to achieve the required temperature boost. The two absorbers are served by one generator. Both open and closed cycle regeneration of the absorbent solution were considered. Two different working fluid combinations (water/lithium bromide and water/lithium chloride), different operating conditions, and variation of selected parameters are presently being investigated.

A. Kramer, D. Mody, S. Ren, R. E. Cowley and J. M. Calm

Food Policy announces a special publ icat ion. . .

N . t r m o - pUmmZ The State of the Art

THE PROCEEDINGS OF MEETINGS HELD AT THE UNIVERSITY OF CALIFORNIA, BERKELEY, 1976-1977 edited by Leonard Joy with the assistance of Christina Wood Major papers: What Economic Planners Need to Know about the Determinants of Nutrition Status Lance Taylor

Recent Developments: Poverty-focused Planning Pranab Bardhan

Sedoral Approaches to Food and Nutrition Policy Analysis: Nutrition and Health Sector Planning Carl Taylor

Also included in this important publication are short presentations and discussions on each keynote paper, and an introduction and summarizing assessment by the editor.

Published by IPC Science and Technology Press Ltd, for the United States Agency for International Development.

275 x 200mm/140 pages November 1978/ISBN 0 86103 007 9~Price £11.50 ($29.90)

IPC Science and Technology Press Umited, PO Box 63, Westbury House, Bury Street, Guildford, Surrey GU2 5BH Telephone (0483) 31261 Telex: 859556 Scitec G

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