 It is of great importance to keep an animal’s environment conducive for maximum production.

 Research has tended to concentrate on genetic improvements to increase milk production and on nutrient supply to the cow during early lactation.

 Excess heat in animal houses can be removed using a heat pump.

Problem statement and analysis

 Most of the heat produced by animals is usually left hanging around the animal making it uncomfortable and affecting its productivity.  Even with ventilation to cool the animal, the heat would still be wasted yet it could be recovered for reheat purposes.

Overall objective

 To design a heat recovery system for an animal house using a heat pump

.

Specific objectives

 To determine how much heat is produced by a cattle unit housing 200 cattle.

 To analyze a heat pump to recover this heat energy  To determine how much heat is recovered from the system and suggest areas where this heat can be used.

SITE ANALYSIS AND INVENTORY

 Area - 30m by 15m with a height of 3m.  Intended holding capacity - 200 Friesian cows  current capacity - 60 cows  Weight per cow - 400kg.  Existing structure is made of concrete, with an open upper half.

 Temperatures of up to 27 0 C, with the coldest months as June, July and part of August with temperatures as low as 14 0 C.

 Energy recovery is a common practice in countries looking to sustainable ways of maintaining cost effective heating and cooling systems.

 Denmark uses centralized heating and cooling systems to lower costs and reduce emissions, with uniquely developed solutions to enable sustainable district heating and cooling.

(www.stateofgreen.htm)



Hot water production with a

Primary goal to make available a supply of hot water 

Heat recovery for hot water production:

Aimed at reducing heating costs by heating water with waste heat recovered from an overheated area which does not otherwise require cooling 

Heat recovery for space cooling:

Employed to cool a space, typically for comfort or product storage and also reduce heating costs by reducing the load on boilers

 Mechanical ventilation with heat recovery (MVHR) systems exchange stale air for fresh air, and recover heat in the process.

 A heat recovery ventilator is a device that extracts heat that would normally be expelled to the atmosphere and transferring this heat to another location like fresh air before it is redistributed.

 A heat pump is a machine or device that moves heat from one location (the 'source'),at a lower temperature, to another location (the 'sink'),at a higher temperature, using mechanical work.

(Cengel and Michael, 2008)

Several factors are considered during the design process, they include;  The climate characteristics of the place where it will be installed e.g. temperature  The type of building i.e. residential, tertiary or industrial buildings.

 Conditions of usage.

 Amount of heat to be produced from the source.

 Heat produced by animals  Refrigerant choice  Heat pump analysis  Amount of energy used by heat pump  Energy produced by heat ump

 Determination of heat produced by the animals per unit weight, Q s .

Q s = N *sensible heat produced per animal*unit weight = 54.8MW



Determination of condenser pressures and operation temperatures Condenser temperatures should be at least

10 °C higher than ambient temperatures

@ 0.2 bar and 1bar pressures At 25 0 C and 0 0 C temperatures Q H heat extracted from heat pump (KJ/Kg)

155.37KJ/Kg

ΔΘ of water at condenser COP

7.4

3.13

Compressor power (KW)

36.7

172.88KJ/Kg 8.3

4.03

26

 The heat pump would recover up to172.88KJ/Kg from an input 26KW  137KJ/Kg heat is produced by a cattle unit housing 200 cattle  The amount of heat recovered from the system would be 172.88KJ/Kg.

 This heat can be used around the farm for cleaning purposes, or expelled from the condenser directly to a calf pen.

 Consider use of a heat pump with vapor injection to allow for reheat of the refrigerant. As it delivers a higher temperature at the condenser and raises the COP of the system.  A modification of the ventilation system would also provide for easier heat recovery from the animal house.

 American Society of Agricultural and Biological Engineers (ASABE) 2009

ASABE standards.

St. Joseph, Michigan, USA.

 American Society of Heating, Refrigeration and Air-conditioning Engineers (ASHRAE). 2005.

ASHRAE Handbook of fundamentals

 Cengel, Y.A. & Michael, A.B. (2008).

Thermodynamics: An Engineering Approach 6 th Ed.

McGraw Hill Inc.

 Eastop, T.D. & McConkey, A. (2009).

Application Thermodynamics for Engineering Technologists. 5 th Ed.

Pearson publication.

 Haines, R.W. & Wilson, C.L. 1994.

HVAC systems design handbook.

New York, USA, McGraw Hill Inc.

 Hellickson, M.A. & Walker, J.N.

Ventilation of Agricultural Structures.

ASAE monograph No. 6. St. Joseph, Michigan, USA.

 Kreider, J.F. 2001.

Handbook of heating, ventilation and air conditioning.

Boca Raton, Florida, USA. CRC Press Ltd.

 Wang, S.K. 2000.

Handbook of air conditioning and refrigeration.

New York, McGraw Hill Inc.



www.heatpumpcentre.org



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