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 cowscurrent capacity - 60 cows Weight per cow - 400kg. Existing structure is made of concrete, with an open upper half.Temperatures of up to 270C, with the coldest months as June, July and part of August with temperatures as low as 140C.

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, Qs.

Qs = 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 250C and 00C temperatures

QH heat extracted from

heat pump (KJ/Kg)

155.37KJ/Kg 172.88KJ/Kg

ΔΘ of water at condenser

7.4 8.3

COP 3.13 4.03

Compressor power (KW)

36.7 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 6th Ed. McGraw Hill Inc.

Eastop, T.D. & McConkey, A. (2009). Application Thermodynamics for Engineering Technologists. 5th 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 www.stateofgreen.htm