ASHRAE Journal - February 2011 - 20

AC Forming Molds Coolers PHE Storage Tunnel Total

487 ton 201 ton 100 ton 73 ton 37 ton 36 ton 34 ton 967 ton

Calorifiers Cookers Bowl Washers Other Users CIP Calorifiers Domestic Hot Water Losses Total

2.811 MBtu/h 2.774 MBtu/h 0.861 MBtu/h 0.515 MBtu/h 0.447 MBtu/h 0.304 MBtu/h 0.945 MBtu/h 8.655 MBtu/h

Table 2: Schedule of cooling loads.

Table 3: Schedule of heating loads.

heat pump system, but it only accounts for about one third pressors provide the base cooling load, with heat rejection to of the total site demand for heating. The cleaning load takes ambient. When heat recovery is required the other two comfresh water at 50°F (10°C) and heats it to 196°F (90°C). In the pressors run at higher discharge pressure, drawing ammonia closed loop heating circuits, for example stopping chocolate from the common evaporator on the glycol cooling circuit. from solidifying in the machines, the water circulates between Therefore, it is possible, with the two independent expansion 104°F and 140°F (40°C and 60°C). valves feeding the gravity-fed receiver, to run the heat recovWhen the cooling and heating loads were compared it was ery circuit at a high discharge pressure and the heat rejection concluded that the most economic installation would only pro- circuit at a much lower discharge pressure. If the cooling devide a portion of the heating by coupling with the cooling sys- mand is high, but there is no requirement for recovered heat, tem. The cooling system was designed with an installed capaci- then the heat recovery compressors are able to deliver gas to ty of 853 tons (3000 kW) but with pumps, vessels and pipework the air cooled condenser through the bypass valves on the dissized for a maximum capacity of 1,023 tons (3600 kW). The charge header, and will then operate more efficiently at reinstalled capacity is less than the total schedule because there duced discharge pressure. is some diversity in the timing of the loads. For example, the To maximize the efficiency of the heat recovery system the air-conditioning load is more significant in the summer and the oil separators on the heat recovery compressors are insulated. forming and molding loads are not continuous. The compressor units can be seen in Photo 1. The heating system was designed to accept water at 140°F The glycol cooling circuit is served by a gravity fed plate (60°C) from the heat recovery circuit. The steam for cookers heat exchanger, which uses a low ammonia charge to achieve is generated by gas boilers and the top-up heating for the other the full cooling and heating requirement. The total ammonia circuits, from 140°F to 194°F (60°C to 90°C) is provided by content of the system is 2,600 lbs (1,200 kg), which is equivathe boilers. This reduces the heat demand from the heat recov- lent to a charge of 2.9 lb/tons (0.375 kg/kW). The additional ery system to a total of 1,230 kW, with 40% going to the once- charge due to the heat recovery is not significant because the through circuit and 60% going to the closed loop. heat recovery part of the circuit uses plate and shell heat exWith this configuration, half of the heating demand is pro- changers. The main proportion of the ammonia charge is held vided by waste heat from the cooling process, and it is only in the air-cooled condensers and in the gravity feed surge necessary to boost the condensing condition of the chillers from the 60°C 60°C standard design of 118°F to 138°F Hot DesuperDesuperAir-Cooled Condenser Process (43°C to 59°C). Heat rejection to CIP Circuit heater heater Circuit atmosphere is through air-cooled condensers designed for a summer Condenser Condenser ambient of 95°F (35°C). In cooler weather the discharge pressure reOil duces to match the ambient condiCooler Subcooler tions, with a minimum condensing condition of 68°F (20°C). When Cold heating is not required by the proGlycol High Pressure Discharge cess, and there is no further storage Circuit Low Pressure Discharge capacity available, the discharge pressure on the heat recovery part of the system drops back to the lowCompressors er figure, making the cooling duty as efficient as possible. Suction The system configuration is shown in Figure 1. Two of the com- Figure 1: Heat recovery circuits.
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February	 2011



ASHRAE Journal - February 2011

Table of Contents for the Digital Edition of ASHRAE Journal - February 2011

ASHRAE Journal - February 2011
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Thermal Coupling of Cooling and Heating Systems
10 Common Problems in Energy Audits
Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
A Guide to Wireless Technologies
Building Sciences
Solar NZEB Project
Emerging Technologies
People
Special Section
InfoCenter
Commissioning
Products
Washington Report
Classified Advertising
Advertisers Index
ASHRAE Journal - February 2011 - ASHRAE Journal - February 2011
ASHRAE Journal - February 2011 - Cover2
ASHRAE Journal - February 2011 - 1
ASHRAE Journal - February 2011 - 2
ASHRAE Journal - February 2011 - Contents
ASHRAE Journal - February 2011 - Commentary
ASHRAE Journal - February 2011 - 5
ASHRAE Journal - February 2011 - Industry News
ASHRAE Journal - February 2011 - 7
ASHRAE Journal - February 2011 - Letters
ASHRAE Journal - February 2011 - 9
ASHRAE Journal - February 2011 - 10
ASHRAE Journal - February 2011 - 11
ASHRAE Journal - February 2011 - 12
ASHRAE Journal - February 2011 - 13
ASHRAE Journal - February 2011 - 14
ASHRAE Journal - February 2011 - 15
ASHRAE Journal - February 2011 - Meetings and Shows
ASHRAE Journal - February 2011 - 17
ASHRAE Journal - February 2011 - Thermal Coupling of Cooling and Heating Systems
ASHRAE Journal - February 2011 - 19
ASHRAE Journal - February 2011 - 20
ASHRAE Journal - February 2011 - 21
ASHRAE Journal - February 2011 - 22
ASHRAE Journal - February 2011 - 23
ASHRAE Journal - February 2011 - 24
ASHRAE Journal - February 2011 - 25
ASHRAE Journal - February 2011 - 10 Common Problems in Energy Audits
ASHRAE Journal - February 2011 - 27
ASHRAE Journal - February 2011 - 28
ASHRAE Journal - February 2011 - 29
ASHRAE Journal - February 2011 - 30
ASHRAE Journal - February 2011 - 31
ASHRAE Journal - February 2011 - 32
ASHRAE Journal - February 2011 - 33
ASHRAE Journal - February 2011 - Hall of Fame Feature: History of the Changing Concepts in Ventilation Requirements
ASHRAE Journal - February 2011 - 35
ASHRAE Journal - February 2011 - 36
ASHRAE Journal - February 2011 - 37
ASHRAE Journal - February 2011 - 38
ASHRAE Journal - February 2011 - 39
ASHRAE Journal - February 2011 - 40
ASHRAE Journal - February 2011 - 41
ASHRAE Journal - February 2011 - 42
ASHRAE Journal - February 2011 - 43
ASHRAE Journal - February 2011 - A Guide to Wireless Technologies
ASHRAE Journal - February 2011 - 45
ASHRAE Journal - February 2011 - 46
ASHRAE Journal - February 2011 - 47
ASHRAE Journal - February 2011 - 48
ASHRAE Journal - February 2011 - 49
ASHRAE Journal - February 2011 - Building Sciences
ASHRAE Journal - February 2011 - 51
ASHRAE Journal - February 2011 - 52
ASHRAE Journal - February 2011 - 53
ASHRAE Journal - February 2011 - 54
ASHRAE Journal - February 2011 - 55
ASHRAE Journal - February 2011 - 56
ASHRAE Journal - February 2011 - 57
ASHRAE Journal - February 2011 - 58
ASHRAE Journal - February 2011 - 59
ASHRAE Journal - February 2011 - 60
ASHRAE Journal - February 2011 - 61
ASHRAE Journal - February 2011 - Solar NZEB Project
ASHRAE Journal - February 2011 - 63
ASHRAE Journal - February 2011 - 64
ASHRAE Journal - February 2011 - 65
ASHRAE Journal - February 2011 - 66
ASHRAE Journal - February 2011 - 67
ASHRAE Journal - February 2011 - 68
ASHRAE Journal - February 2011 - 69
ASHRAE Journal - February 2011 - Emerging Technologies
ASHRAE Journal - February 2011 - 71
ASHRAE Journal - February 2011 - 72
ASHRAE Journal - February 2011 - 73
ASHRAE Journal - February 2011 - 74
ASHRAE Journal - February 2011 - 75
ASHRAE Journal - February 2011 - People
ASHRAE Journal - February 2011 - 77
ASHRAE Journal - February 2011 - InfoCenter
ASHRAE Journal - February 2011 - 79
ASHRAE Journal - February 2011 - 80
ASHRAE Journal - February 2011 - 81
ASHRAE Journal - February 2011 - 82
ASHRAE Journal - February 2011 - 83
ASHRAE Journal - February 2011 - 84
ASHRAE Journal - February 2011 - 85
ASHRAE Journal - February 2011 - Commissioning
ASHRAE Journal - February 2011 - 87
ASHRAE Journal - February 2011 - 88
ASHRAE Journal - February 2011 - 89
ASHRAE Journal - February 2011 - 90
ASHRAE Journal - February 2011 - Products
ASHRAE Journal - February 2011 - Washington Report
ASHRAE Journal - February 2011 - Classified Advertising
ASHRAE Journal - February 2011 - 94
ASHRAE Journal - February 2011 - 95
ASHRAE Journal - February 2011 - Advertisers Index
ASHRAE Journal - February 2011 - Cover3
ASHRAE Journal - February 2011 - Cover4
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