Evaporative coolers and condensersEvaporative coolers and condensers operated in winter may provide adequate operated in winter may provide adequate capacity when operated with dry coils.
capacity when operated with dry coils.
Maintenance, water and electrical costs Maintenance, water and electrical costs can be reduced. Heat tracing and pan can be reduced. Heat tracing and pan heaters can be turned off. The detrimental heaters can be turned off. The detrimental
Maintain maximum heat transfer rates by Maintain maximum heat transfer rates by effect of icing on
effect of icing on equipment and buildingsequipment and buildings
minimizing fouling. Consider the condenser water minimizing fouling. Consider the condenser water is eliminated. Note that the reduced
is eliminated. Note that the reduced
system in Housekeeping Worked Example 2.
system in Housekeeping Worked Example 2.
power requirements for fan and circulating power requirements for fan and circulating
Assume that half the change in performance was Assume that half the change in performance was pumps in cooling towers and evaporative
pumps in cooling towers and evaporative
because of condenser cleaning.
because of condenser cleaning.
coolers may be offset by a
coolers may be offset by a COP decreaseCOP decrease caused by higher condenser temperatures.
Consider a new heat pump system Consider a new heat pump system insteadinstead of a new air
of a new air conditioning system, if winter conditioning system, if winter An automatic water treatment system wasAn automatic water treatment system was heating is required. The higher equipment
heating is required. The higher equipment provided for the cooling tower, to provided for the cooling tower, to optimize water optimize water cost will be offset by reduced heating costs
cost will be offset by reduced heating costs make-up and blowdown, and automatically feedmake-up and blowdown, and automatically feed during the winter season.
during the winter season. chemicals to control fouling. Capital cost waschemicals to control fouling. Capital cost was R3,000. Annual chemical costs are estimated at R3,000. Annual chemical costs are estimated at
Provide lockable covers on automaticProvide lockable covers on automatic
R800. Note that the system must be cleaned before R800. Note that the system must be cleaned before controls and thermostats, to prevent
controls and thermostats, to prevent
automatic water treatment is initiated. normally goes to drain for evaporative
normally goes to drain for evaporative
=1.8 yrs
=1.8 yrs condenser or cooling tower make-up
condenser or cooling tower make-up water. While not conserving energy, this
water. While not conserving energy, this At the end of the first year, the cost of cleaning theAt the end of the first year, the cost of cleaning the will reduce operating costs.
will reduce operating costs. exchangers, the cooling tower, and providingexchangers, the cooling tower, and providing
Re-evaluate the use of hot gas bypassRe-evaluate the use of hot gas bypass condenser water treatment is negligible. Seecondenser water treatment is negligible. See when a refrigeration unit works at
part-when a refrigeration unit works at part- Housekeeping Worked Example 2.Housekeeping Worked Example 2.
load for any significant period. It may be load for any significant period. It may be
Other costs are reduced. Annual cleaning of Other costs are reduced. Annual cleaning of possible to eliminate the bypass feature
possible to eliminate the bypass feature
exchangers is eliminated and
exchangers is eliminated and controlled blowdowcontrolled blowdownn and cycle or turn off the refrigeration
5.2.1.1 WATER TREATMENT FOR 5.2.1.1 WATER TREATMENT FOR
CONDENSER WATER
CONDENSER WATER
5.2.1.2
A small office addition is planned for an industrial
A small office addition is planned for an industrial A small manufacturing plant has a 90 A small manufacturing plant has a 90 kW capacity kW capacity facility in Cape Town. An economical means of
facility in Cape Town. An economical means of refrigeration plant operating at a COP of 3. Therefrigeration plant operating at a COP of 3. The heating and cooling the addition is desirable. The
heating and cooling the addition is desirable. The compressor has six cylinders and operates at full-compressor has six cylinders and operates at full-plant rejects waste heat in the form of warm water.
plant rejects waste heat in the form of warm water. load 24 hours per day, 5 days per week and 50load 24 hours per day, 5 days per week and 50 Loads for the proposed building, including
Loads for the proposed building, including weeks per year. During weekends the refrigerationweeks per year. During weekends the refrigeration ventilation, are 35.17 kW cooling, and 29.31 kW
ventilation, are 35.17 kW cooling, and 29.31 kW load is less than 10 per cent load is less than 10 per cent of full-load, and the unitof full-load, and the unit heating. A rooftop packaged air conditioning
heating. A rooftop packaged air conditioning uses hot gas bypass to avoid low suction pressuresuses hot gas bypass to avoid low suction pressures system with electric heating is proposed. The
system with electric heating is proposed. The and evaporator frosting. It is proposed to eliminateand evaporator frosting. It is proposed to eliminate estimated annual heating cost for the all-electric
estimated annual heating cost for the all-electric hot gas bypass and cycle the unit on and off hot gas bypass and cycle the unit on and off to meetto meet system is R2 45l.
system is R2 45l. the low loads. Controls will be modified to the low loads. Controls will be modified to eliminate hot gas bypass and install anti-short cycle eliminate hot gas bypass and install anti-short cycle A water-to-air heat pump was considered as an
A water-to-air heat pump was considered as an
timers at a cost of R1400. The hot gas bypass timers at a cost of R1400. The hot gas bypass alternative to the basic, air-conditioning with
alternative to the basic, air-conditioning with
imposes a cooling load of about 33 per cent on imposes a cooling load of about 33 per cent on thethe electric heat, rooftop package initially proposed.
electric heat, rooftop package initially proposed.
unit at a cost of
unit at a cost of R1188 per year. In addition to theR1188 per year. In addition to the The heat pump was selected to meet the design
The heat pump was selected to meet the design
cost of providing the 9 kW cooling load, by cost of providing the 9 kW cooling load, by heating and cooling loads, with electric duct
heating and cooling loads, with electric duct heatersheaters
eliminating hot gas bypass, this R1188 can be saved.
eliminating hot gas bypass, this R1188 can be saved.
for 100 per cent backup. The COP for heating at for 100 per cent backup. The COP for heating at the given water condition was 2.25 and similar to the given water condition was 2.25 and similar to
SSiimmpplle e ppaayybbaacckk == RR1 1 440000//RR1 1 118888 the air-conditioner performance in the summer.
the air-conditioner performance in the summer.
=
= 11..2 2 yyeeaarrss The source of warm water was available 85 per
The source of warm water was available 85 per cent of the time during the heating season, and cent of the time during the heating season, and cooling water was available throughout the cooling cooling water was available throughout the cooling season.
Implemented retrofit opportunities are defined as Implemented retrofit opportunities are defined as +(0.15xR2451)
+(0.15xR2451)
energy management actions that are done once, energy management actions that are done once, and and
=
= 1 1 229944
for which the cost is significant.
for which the cost is significant. Many of theMany of the opportunities in this category will require detailed opportunities in this category will require detailed A
Annnnuuaal l ssaavviinnggss == RR2 2 445511- - RR1 1 229944
analysis by specialists and cannot be examined in analysis by specialists and cannot be examined in
=
= RR1 1 115577
detail in this guide. The
detail in this guide. The following are typical Energy following are typical Energy The extra cost for a heat pump package over
The extra cost for a heat pump package over Management Opportunities in the RetrofitManagement Opportunities in the Retrofit standard air conditioning with electric heat is
standard air conditioning with electric heat is category.category.
estimated at R 3 000 estimated at R 3 000
Absorption equipment can provide lowAbsorption equipment can provide low cost cooling if dependable, high grade
Use Use a a heat heat pump pump to to upgrade upgrade the the low low superheat superheat can can be be used used where where lower lower temperature
temperature waste waste heat heat to to a a temperature temperature temperature temperature latent latent heat heat cannot. cannot. Care Care mustmust ssuuiittaabblle e ffoor r bbuuiillddiinng g hheeaattiinngg.. bbe e ttaakkeen n iin n tthhe e ddeessiiggn n oof f tthhe e rreeffrriiggeerraanntt
Provide Provide a a thermal thermal storage storage system system to to piping piping system system to to ensure ensure proper proper return return of of reduce
reduce compressor compressor cycling, cycling, and and allow allow liquiliquid d refrrefrigeraigerant nt and and oil oil frfr om om thethe continuous
continuous operation operation at at full-load full-load and and desuperheater.desuperheater.
higher efficiency.
higher efficiency. Use well, river or lake water as a lower Use well, river or lake water as a lower
Provide Provide decentralized decentralized systems systems to to match match temperature cooling temperature cooling medium medium to to reducereduce loads
loads with with specialized specialized requirements. requirements. For For condensing condensing temperatures. temperatures. If If an an air-cooledair-cooled example,
example, if if a a large large system system operates operates at at a a low low condenser requires major repair or condenser requires major repair or ev
evapapororatator or tetempmpererataturure e whwhen en ononly ly a a smsmalall l rere plpl acac emem ee ntnt , , coco nn sisi dede r r usus inin g g anan portio
portion n of of the the load load requirequires res low low evaeva porapora tivtiv e e condcond ensens er. er. ImprImpr ovedoved temper
temper ature, ature, providprovid e e a a ssmall, mall, llow ow perfoperformancrmance e and and reducreduced ed energenergy y costcost temperature
temperature system system to to serve serve the the special special because because of of the the higher higher COP COP may may justify justify thethe area.
area. Operate Operate the the large large system system at at a a higher higher added added expenditure.expenditure.
evaporator temperature to improve COP.
evaporator temperature to improve COP. Use mechanical refrigeration equipment inUse mechanical refrigeration equipment in Co
Co nsns idid er er "p"p igig gygy baba ckck inin g" g" thth e e lolo w w facfaciliilitieties, s, sucsuch h as as indindoooor r swswimmimming ing poopoolsls temperature
temperature system system onto onto the the higher higher where where high high ventilation ventilation rates rates are are requiredrequired te
te mm pp ee rr aa tt uu rr e e sysy ss tt ee m m tt o o rr ee dd uu cc e e fofor r huhumimididity ty cocontntrorol. l. WiWintnter er heheatatining g cocoststss temperature
temperature differences differences and and increase increase for for the the ventilation ventilation air air can can be be reduced reduced by by C
COOPP.. rreedduucciinng g tthhe e vveennttiillaattiioon n rraattee. . TThhe e ttoottaal l hheeaatt
Reclaim Reclaim rejected rejected condenser condenser heat heat for for space space of of rejection rejection can can be be used used to to preheat preheat thethe hea
heatintin g, g, proprocescess s heaheatintin g g or or water water ventiventilatiolation n suppsupply ly air air and and prehpreheat eat thethe preheating.
preheating. In In addition addition to to reclaiming reclaiming the the make-up water make-up water for for the the pool. pool. Energy Energy savingssavings otherwise
otherwise wasted wasted heat, heat, the the system system COP COP result.result.
may be increased when a lower may be increased when a lower temp
temp eraterat ure ure condcond ensiensi ng ng medimedi um um is is Calculations Calculations for for 'retrofit' 'retrofit' savings savings are are site site specific specific andand avai
avai labllabl e. e. For For exexamplampl e, e, prpreheaehea titing ng in in many many casecases s invoinvolve lve detaidetailed led analyanalysis. sis. This This bookbookletlet domestic
domestic water water will will reduce reduce the the energy energy serves serves as as a a guide guide for for the the possible possible avenues avenues toto required
required for for water water heating heating and and reduce reduce the the investigate investigate and and gives gives a a feel feel for for energy energy efficiency efficiency con
condenden sinsing g temtem perperatuatu re. re. The The colcold d earniearning ng oppoopportunirtunities ties in in refrirefrigerageration tion and and coolcooling.ing.
incoming water supply can often reduce incoming water supply can often reduce the condensing water temperature by 5 to the condensing water temperature by 5 to 10ºC, thereby increasing the system COP.
10ºC, thereby increasing the system COP.
Desuperheat the refrigerant vapour (hotDesuperheat the refrigerant vapour (hot gas) leaving the compressor. The gas) leaving the compressor. The superheat can be recovered for process or superheat can be recovered for process or make-up water preheating. Because the make-up water preheating. Because the temperature of the hot gas is higher than temperature of the hot gas is higher than the condensing temperature, the the condensing temperature, the